Title of Invention: METHOD AND APPARATUS FOR ACCESSING OTT APPLICATION AND PUSHING MESSAGE BY SERVER Abstract: In the field of communications technologies, a method and an apparatus for accessing an OTT application are disclosed. By using the accessing method, a user can access multiple OTT applications by using one piece of first user information, and therefore, the user does not need to record first user information separately for each OTT application, so as to reduce complexity of accessing multiple OTT applications. Three types of methods and apparatuses for pushing a message by a server are further provided. By using the message pushing methods, a server can push a message to a terminal that registers but does not enable a related OTT application, and the server can also push a message to a terminal that does not register a corresponding OTT application, so that a terminal does not need to receive a message only if a related OTT application is enabled. Detailed Description: CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of International Application No. PCT/CN2014/082275, filed on Jul. 15, 2014, which claims priority to Chinese Patent Application No. 201310354163.5, filed on Aug. 14, 2013, both of which are hereby incorporated by reference in their entireties. TECHNICAL FIELD Embodiments of the present invention relate to the field of communications technologies, and in particular, to a method and an apparatus for accessing an OTT application and pushing a message by a server. BACKGROUND With rapid development of over the top (OTT) applications, an increasingly high quantity of OTT applications appear currently, where the OTT applications refer to services developed by Internet enterprises by using a broadband network of an operator, for example, an instant messaging service and applications in various mobile application stores, and all these are OTT applications. Currently, many OTT applications are respectively developed based on different servers. Different OTT applications each have a specific user group. In addition, these OTT applications developed based on different servers cannot use a same user account number, that is, different OTT applications can only use their respective user account numbers to access corresponding OTT servers, and a server corresponding to a different OTT application can only send a message to a terminal that is registered on the server. In an actual application, the prior art has the following disadvantages: a: As OTT applications increase, each time when a new OTT application is accessed, registration needs to be performed on a corresponding server to obtain corresponding user account number and password information (which are collectively referred to as first user information), and then access can be performed. The new OTT application cannot be accessed by using user account number and password information that are corresponding to another successfully registered OTT application, which is specifically shown in FIG. 1A. Therefore, there exists a problem that access to multiple OTT applications is complex. b: A server can only push a message (such as news information and weather information) to a terminal that is registered on the server and enable a corresponding OTT application, but cannot push the message to a terminal that does not register the corresponding OTT application or does not enable the corresponding OTT application, but registers and enables another OTT application, which is specifically shown in FIG. 1B. Therefore, there exists a problem that a push manner and a push occasion are relatively undiversified when the server pushes a corresponding message to the corresponding OTT application. SUMMARY Embodiments of the present invention provide a method and an apparatus for accessing an OTT application, so as to resolve a problem existing in the prior art that access to multiple OTT applications is complex. The embodiments of the present invention further provide a method and an apparatus for pushing a message by a server, so as to resolve a problem existing in the prior art that a push manner and a push occasion are relatively undiversified when a server pushes a message. According to a first aspect, a method for accessing an OTT application is provided, including: storing, by an interworking server, acquired first user information used by a user to register an OTT application, where the first user information is used by the user to access at least two OTT applications; receiving, by the interworking server, second user information that is used by the user when the user accesses the OTT application; and determining, by the interworking server, whether the first user information matches the second user information, and if the first user information matches the second user information, allowing access of the user, or indicating that authentication of the user succeeds, so that the user accesses a server that is corresponding to an OTT application to be accessed; or if the first user information does not match the second user information, prohibiting access of the user, or indicating that authentication of the user fails, so that a server that is corresponding to an OTT application to be accessed rejects the access of the user. With reference to the first aspect, in a first possible implementation manner, acquiring, by the interworking server, the first user information that is used by the user to register the OTT application includes: if the user registers an OTT account by using the interworking server, directly acquiring, by the interworking server, the first user information; or if the user registers an OTT account by using a server corresponding to the OTT application, acquiring, by the interworking server, the first user information by using the user, or acquiring, by the interworking server, the first user information by using the server corresponding to the OTT application. With reference to the first aspect or the first possible implementation manner of the first aspect, in a second possible implementation manner, after receiving the first user information that is used by the user to register the OTT application, and before storing the first user information, the interworking server receives a password corresponding to the first user information. With reference to the first aspect or the first to the second possible implementation manners of the first aspect, in a third possible implementation manner, the receiving, by the interworking server, second user information that is carried by the user when the user accesses the OTT application includes: receiving, by the interworking server by using a client corresponding to the server, second user information provided by the client when the user accesses the OTT application; or acquiring, by the interworking server by using a request that is redirected to the interworking server by the server that is corresponding to the OTT application to be accessed, second user information that is provided when the user accesses a second OTT application; or receiving, by the interworking server, second user information sent by the server that is corresponding to the OTT application to be accessed, where when the user accesses a second OTT application, the second user information is provided to the server corresponding to the OTT application. With reference to the first aspect or the first to the second possible implementation manners of the first aspect, in a fourth possible implementation manner, after it is determined that the second user information is the first user information stored by the server, and when it is determined that a security level of the second user information reaches a preset security level threshold, the access of the user is allowed, or it indicates that the authentication of the user succeeds, so that the user accesses the server that is corresponding to the OTT application to be accessed. According to a second aspect, a method for pushing a message by a server corresponding to an OTT application is provided, including: receiving a cross-OTT message push request that is sent by a server corresponding to a first OTT application, where the cross-OTT message push request is used by the server corresponding to the first OTT application to send a message to a user that does not access the first OTT application or does not register the first OTT application; and selecting, according to stored and acquired user information for registering an OTT application, a cross-OTT information receiving user that receives the message sent by the server corresponding to the first OTT application, and sending a message that is to be sent by the server corresponding to the first OTT application. With reference to the second aspect, in a first possible implementation manner, the selecting a cross-OTT information receiving user that receives the message sent by the server corresponding to the first OTT application specifically includes: acquiring intention information of a user corresponding to the stored user information, and obtaining, according to the intention information of the user, a type of information that the user intends to receive; and selecting a user whose type of information that the user intends to receive matches a type of a message pushed by the first OTT application, as a cross-OTT information receiving user of the message that is to be sent by the server corresponding to the first OTT application. With reference to the second aspect or the first possible implementation manner of the second aspect, in a second possible implementation manner, the sending a message that is to be sent by the server corresponding to the first OTT application includes: for each determined cross-OTT information receiving user, sending, by using a server accessed by the cross-OTT information receiving user, the received message that is sent by the server corresponding to the first OTT application, or directly sending the received message that is sent by the server corresponding to the first OTT application. With reference to the second possible implementation manner of the second aspect, in a third possible implementation manner, for each determined cross-OTT information receiving user, after the received message that is sent by the server corresponding to the first OTT application is acquired, and before the received message is sent to the cross-OTT information receiving user by using the server accessed by the cross-OTT information receiving user, acquired access information of the cross-OTT information receiving user is stored. With reference to the third possible implementation manner of the second aspect, in a fourth possible implementation manner, acquiring the access information of the cross-OTT information receiving user specifically includes: if the cross-OTT information receiving user accesses another server, receiving access information that is sent by the server accessed by the cross-OTT information receiving user; or if the cross-OTT information receiving user accesses the server, acquiring the access information of the cross-OTT information receiving user directly from the server. According to a third aspect, a method for pushing a message by a server corresponding to an OTT application is provided, including: receiving a cross-OTT message push request that is sent by a server corresponding to a first OTT application, where the cross-OTT message push request is used by the server corresponding to the first OTT application to send a message to a user that registers but does not access the first OTT application or does not register the first OTT application; and selecting, according to stored and acquired user information for registering an OTT application, a cross-OTT information receiving user that receives the message sent by the server corresponding to the first OTT application, and sending information about the selected cross-OTT information receiving user to the server corresponding to the first OTT application, so that the server corresponding to the first OTT application sends to-be-pushed information to the selected cross-OTT information receiving user. According to a fourth aspect, a method for pushing a message by a server corresponding to an OTT application is provided, including: acquiring, according to stored and acquired user information for accessing an OTT application, OTT information including at least user access information; and sending the acquired OTT information to a server corresponding to the first OTT application, so that the server corresponding to the first OTT application determines a cross-OTT information receiving user to which a message is to be pushed, and pushes the to-be-pushed message to the cross-OTT information receiving user. With reference to the fourth aspect, in a first possible implementation manner, the acquired OTT information further includes: intention information of a user, where the intention information of the user carries at least a type of information that the user intends to receive. According to a fifth aspect, an interworking server is provided, including: an information storage module, configured to store acquired first user information used by a user to register an OTT application, where the first user information is used by the user to access at least two OTT applications; an information acquiring module, configured to receive second user information that is used by the user when the user accesses the OTT application; and a determining module, configured to determine whether the first user information matches the second user information, and if the first user information matches the second user information, allow access of the user, or indicate that authentication of the user succeeds, so that the user accesses a server that is corresponding to an OTT application to be accessed; or if the first user information does not match the second user information, prohibit access of the user, or indicate that authentication of the user fails, so that a server that is corresponding to an OTT application to be accessed rejects the access of the user. With reference to the fifth aspect, in a first possible implementation manner, the information storage module is specifically configured to: if the user registers an OTT account by using the interworking server, directly acquire the first user information; or if the user registers an OTT account by using a server corresponding to the OTT application, acquire the first user information by using the user, or acquire the first user information by using the server corresponding to the OTT application. With reference to the fifth aspect or the first possible implementation manner of the fifth aspect, in a second possible implementation manner, the information storage module is further configured to: after receiving the first user information that is used by the user to register the OTT application, and before storing the first user information, receive a password corresponding to the first user information. With reference to the fifth aspect or the first to the second possible implementation manners of the fifth aspect, in a third possible implementation manner, the information acquiring module is specifically configured to: receive, by using a client corresponding to the server, second user information provided by the client when the user accesses the OTT application; or acquire, by using a request that is redirected to the server by the server that is corresponding to the OTT application to be accessed, second user information that is provided when the user accesses a second OTT application; or receive second user information sent by the server that is corresponding to the OTT application to be accessed, where when the user accesses a second OTT application, the second user information is provided to the server corresponding to the OTT application. With reference to the fifth aspect or the first to the second possible implementation manners of the fifth aspect, in a fourth possible implementation manner, the determining module is further configured to: after it is determined that the second user information is the first user information stored by the server, and when it is determined that a security level of the second user information reaches a preset security level threshold, allow the access of the user, or indicate that the authentication of the user succeeds, so that the user accesses the server that is corresponding to the OTT application to be accessed. According to a sixth aspect, an interworking server is provided, including: a first receiving module, configured to receive a cross-OTT message push request that is sent by a server corresponding to a first OTT application, where the cross-OTT message push request is used by the server corresponding to the first OTT application to send a message to a user that does not access the first OTT application or does not register the first OTT application; and a sending module, configured to select, according to stored and acquired user information for registering the OTT application, a cross-OTT information receiving user that receives the message sent by the server corresponding to the first OTT application, and send a message that is to be sent by the server corresponding to the first OTT application. With reference to the sixth aspect, in a first possible implementation manner, the sending module is specifically configured to: acquire intention information of a user corresponding to the stored user information, and obtain, according to the intention information of the user, a type of information that the user intends to receive; and select a user whose type of information that the user intends to receive matches a type of a message pushed by the first OTT application, as a cross-OTT information receiving user of the message that is to be sent by the server corresponding to the first OTT application. With reference to the sixth aspect or the first possible implementation manner of the sixth aspect, in a second possible implementation manner, the sending module is specifically configured to: for each determined cross-OTT information receiving user, send, by using a server accessed by the cross-OTT information receiving user, the received message that is sent by the server corresponding to the first OTT application, or directly send the received message that is sent by the server corresponding to the first OTT application. With reference to the second possible implementation manner of the sixth aspect, in a third possible implementation manner, the sending module is further configured to: for each determined cross-OTT information receiving user, after the received message that is sent by the server corresponding to the first OTT application is acquired, and before the received message is sent to the cross-OTT information receiving user by using the server accessed by the cross-OTT information receiving user, store acquired access information of the cross-OTT information receiving user. With reference to the third possible implementation manner of the sixth aspect, in a fourth possible implementation manner, the sending module is specifically configured to: if the cross-OTT information receiving user accesses another server, receive access information that is sent by the server accessed by the cross-OTT information receiving user; or if the cross-OTT information receiving user accesses the server, acquire the access information of the cross-OTT information receiving user directly from the server. According to a seventh aspect, an interworking server is provided, including: a second receiving module, configured to receive a cross-OTT message push request that is sent by a server corresponding to a first OTT application, where the cross-OTT message push request is used by the server corresponding to the first OTT application to send a message to a user that registers but does not access the first OTT application or does not register the first OTT application; and an information determining module, configured to select, according to stored and acquired user information for registering the OTT application, a cross-OTT information receiving user that receives the message sent by the server corresponding to the first OTT application, and send information about the selected cross-OTT information receiving user to the server corresponding to the first OTT application, so that the server corresponding to the first OTT application sends to-be-pushed information to the selected cross-OTT information receiving user. According to an eighth aspect, an interworking server is provided, including: an acquiring module, configured to acquire, according to stored and acquired user information for accessing an OTT application, OTT information including at least user access information; and an information sending module, configured to send the acquired OTT information to a server corresponding to the first OTT application, so that the server corresponding to the first OTT application determines a cross-OTT information receiving user to which a message is to be pushed, and pushes the to-be-pushed message to the cross-OTT information receiving user. With reference to the eighth aspect, in a first possible implementation manner, the OTT information acquired by the acquiring module further includes: intention information of a user, where the intention information of the user carries at least a type of information that the user intends to receive. Beneficial effects of the present invention are as follows: In the embodiments of the present invention, to resolve a problem existing in the prior art that access to multiple OTT applications is complex, a method and an apparatus for accessing an OTT application are disclosed. By using the accessing method, a user can access multiple OTT applications by using one piece of first user information, and therefore, the user does not need to record first user information separately for each OTT application, so as to reduce complexity of accessing multiple OTT applications. To resolve a problem existing in the prior art that a push manner and a push occasion are relatively undiversified when a server pushes a message, three types of methods and apparatuses for pushing a message by a server are further provided. By using the message pushing methods, a server can push a message to a terminal that registers but does not enable a related OTT application, and the server can also push a message to a terminal that does not register a corresponding OTT application, so that a terminal is not limited to receiving the message only if a related OTT application is enabled. Therefore, the problem existing in the prior art that a push manner and a push occasion are relatively undiversified when a server pushes a message is resolved. BRIEF DESCRIPTION OF DRAWINGS FIG. 1A is a schematic diagram of accessing multiple OTT applications by a terminal in the prior art; FIG. 1B is a schematic diagram of pushing a message by a server corresponding to an OTT application in the prior art; FIG. 1C is a schematic diagram of accessing multiple OTT applications by a terminal, and pushing a message by a server corresponding to an OTT application according to an embodiment of the present invention; FIG. 2 is a detailed flowchart of accessing an OTT application according to an embodiment of the present invention; FIG. 3A is a first schematic diagram of registering an OTT application according to an embodiment of the present invention; FIG. 3B is a second schematic diagram of registering an OTT application according to an embodiment of the present invention; FIG. 3C is a third schematic diagram of registering an OTT application according to an embodiment of the present invention; FIG. 3D is a fourth schematic diagram of registering an OTT application according to an embodiment of the present invention; FIG. 3E is a fifth schematic diagram of registering an OTT application according to an embodiment of the present invention; FIG. 3F is a schematic diagram of setting first user information and a corresponding OTT application according to an embodiment of the present invention; FIG. 4A is a first detailed flowchart of pushing a message by a server corresponding to an OTT application according to an embodiment of the present invention; FIG. 4B is a second detailed flowchart of pushing a message by a server corresponding to an OTT application according to an embodiment of the present invention; FIG. 4C is a third detailed flowchart of pushing a message by a server corresponding to an OTT application according to an embodiment of the present invention; FIG. 5 is a first embodiment of pushing a message by a server corresponding to an OTT application according to an embodiment of the present invention; FIG. 6 is a second embodiment of pushing a message by a server corresponding to an OTT application according to an embodiment of the present invention; FIG. 7 is a first schematic diagram of an interworking server according to an embodiment of the present invention; FIG. 8 is a second schematic diagram of an interworking server according to an embodiment of the present invention; FIG. 9 is a third schematic diagram of an interworking server according to an embodiment of the present invention; and FIG. 10 is a fourth schematic diagram of an interworking server according to an embodiment of the present invention. DESCRIPTION OF EMBODIMENTS To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following clearly describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. The term “and/or” in this specification describes only an association relationship for describing associated objects and represents that three relationships may exist. For example, A and/or B may represent the following three cases: Only A exists, both A and B exist, and only B exists. In addition, the character “/” in this specification generally indicates an “or” relationship between the associated objects. To resolve a problem existing in the prior art that access to multiple OTT applications is complex, a method for accessing an OTT application is provided in embodiments of the present invention, which is specifically: storing, by an interworking server, acquired first user information used by a user to register an OTT application, where the first user information is used by the user to access at least two OTT applications; receiving, by the interworking server, second user information that is used by the user when the user accesses the OTT application; and determining, by the interworking server, whether the first user information matches the second user information, and if the first user information matches the second user information, allowing access of the user, or indicating that authentication of the user succeeds, so that the user accesses a server that is corresponding to an OTT application to be accessed; or if the first user information does not match the second user information, prohibiting access of the user, or indicating that authentication of the user fails, so that a server that is corresponding to an OTT application to be accessed rejects the access of the user. By using the accessing method, a user can access multiple OTT applications by using one piece of first user information, so that the user does not need to record first user information separately for each OTT application, so as to reduce complexity of accessing multiple OTT applications. To resolve a problem existing in the prior art that a push manner and a push occasion are relatively undiversified when a server pushes a message, the embodiments of the present invention further provide three types of methods and apparatuses for pushing a message by a server. One type is: receiving a cross-OTT message push request that is sent by a server corresponding to a first OTT application, where the cross-OTT message push request is used by the server corresponding to the first OTT application to send a message to a user that does not access the first OTT application or does not register the first OTT application; and selecting, according to stored and acquired user information for registering an OTT application, a cross-OTT information receiving user that receives the message sent by the server corresponding to the first OTT application, and sending a message that is to be sent by the server corresponding to the first OTT application. Another type is: receiving a cross-OTT message push request that is sent by a server corresponding to a first OTT application, where the cross-OTT message push request is used by the server corresponding to the first OTT application to send a message to a terminal that registers but does not access the first OTT application or does not register the first OTT application; and selecting, according to stored and acquired user information for registering an OTT application, a cross-OTT information receiving user that receives the message sent by the server corresponding to the first OTT application, and sending information about the selected cross-OTT information receiving user to the server corresponding to the first OTT application, so that the server corresponding to the first OTT application sends to-be-pushed information to the selected cross-OTT information receiving user. By using the message pushing method, a server can push a message to a terminal that registers but does not enable a related OTT application, and the server can also push a message to a terminal that does not register a corresponding OTT application, so that a terminal does not need to receive a message only if a related OTT application is enabled. Therefore, the problem existing in the prior art that a push manner and a push occasion are relatively undiversified when a server pushes a message is resolved. Still another type is: acquiring, according to stored and acquired user information for accessing an OTT application, OTT information including at least user access information; and sending the acquired OTT information to a server corresponding to the first OTT application, so that the server corresponding to the first OTT application determines a cross-OTT information receiving user to which a message is to be pushed, and pushes the to-be-pushed message to the cross-OTT information receiving user. By using the message pushing method, a server can push a message to a terminal that registers but does not enable a related OTT application, and the server can also push a message to a terminal that does not register a corresponding OTT application, so that a terminal does not need to receive a message only if a related OTT application is enabled. Therefore, the problem existing in the prior art that a push manner and a push occasion are relatively undiversified when a server pushes a message is resolved. In the following, preferred implementation manners of the present invention are described in detail with reference to the accompanying drawings. First, description is provided for how to access an unregistered OTT application by a terminal by using an interworking server, and then description is provided for how to receive, by a terminal by using an interworking server, a message sent by a server corresponding to an unregistered OTT application or a server corresponding to an OTT application that is registered but not enabled. As shown in FIG. 1C, before a user terminal accesses an OTT application, an interworking server first needs to store first user information of a user of an OTT application registered by the user terminal. Then, when the user terminal accesses an OTT application that is not registered by the user, the interworking server needs to authenticate user information provided by the user terminal, so as to determine whether the user is allowed to access the OTT application that is not registered by the user, and the OTT application that is not registered by the user accepts or rejects access of the user according to an authentication result. In addition, when a server corresponding to an OTT application that is not accessed by a user needs to push a message (such as advertisement information) to the user, the interworking server needs to determine a cross-OTT information receiving user to which the message is to be pushed, and forward the to-be-pushed message to each cross-OTT information receiving user or a server accessed by the cross-OTT information receiving user. Alternatively, the interworking server sends information (which includes at least account number information, and may further include user access status information) about a cross-OTT information receiving user to an OTT application server that pushes the message. The OTT application server sends the message to each cross-OTT information receiving user or a server accessed by each cross-OTT information receiving user, where the server further sends the message to each cross-OTT information receiving user. Referring to FIG. 2, in an embodiment of the present invention, a detailed flowchart of accessing an OTT application is as follows: Step 200: An interworking server stores acquired first user information used by a user to register an OTT application, where the first user information is used by the user to access at least two OTT applications. Step 210: The interworking server receives second user information that is used by the user when the user accesses the OTT application. Step 220: The interworking server determines whether the first user information matches the second user information; if the first user information matches the second user information, perform step 230, or if the first user information does not match the second user information, perform step 240. Step 230: Allow access of the user, or indicate that authentication of the user succeeds, so that the user accesses a server that is corresponding to an OTT application to be accessed. Step 240: Prohibit access of the user, or indicate that authentication of the user fails, so that a server that is corresponding to an OTT application to be accessed rejects the access of the user. In this embodiment of the present invention, the first user information mainly refers to OTT application account information of the user, where the OTT application account information includes at least OTT application account number information. In addition, other information may be further included, for example, subscription intention of the user, mobile phone number information, email address information, or other contact information. In this embodiment of the present invention, the first user information is acquired by the interworking server in multiple manners. For example, the user submits an OTT account registration application by using a server corresponding to an OTT application; then, the user sends the first user information to the interworking server after registration is completed, or a server corresponding to a successfully registered OTT application sends the first user information to the interworking server. For another example, when the user is registering an OTT account on the interworking server, the interworking server may directly acquire the first user information used by the user to register the OTT application. The first user information in the foregoing manners includes information input by the user, and/or information allocated by the interworking server after the user inputs other information. In the foregoing process, when the user is registering the OTT account on the interworking server, as shown in FIG. 3A, the user may directly enter a specified registration page by using a client corresponding to the interworking server, and then submit the OTT account registration application on the specified registration page. As shown in FIG. 3B, the user may also enter the specified registration page by using a browser client, and then submit the OTT account registration application on the specified registration page. As shown in FIG. 3C, the user may also enter the specified registration page by means of redirection to the interworking server by using a server corresponding to an OTT application to be registered, and then submit the OTT account registration application on the specified registration page. As shown in FIG. 3D, the user may also enter, by using the browser client, a selection interface for registering an OTT application, then select an OTT application on the selection interface for registering an OTT application, so as to enter a specified interface for registering the selected OTT application, and then submit the OTT account registration application on the specified interface. For another example, as shown in FIG. 3E, the user submits the registration application by using a server corresponding to an OTT application, and after registration is completed, the user notifies the interworking server of the first user information, or the server corresponding to the registered OTT application notifies the interworking server of the first user information. To improve security of the first user information, in this embodiment of the present invention, after registering the OTT application, the user may further set password information corresponding to the first user information. In this embodiment of the present invention, the first user information is set to be capable of being used to access more than two OTT applications, which may be set according to the user or by default. When the first user information is set according to the user, a specified registration interface may be entered by using a browser, and a list of names of OTT that may be selected by the user and that may share the first user information is provided on the registration interface. As shown in FIG. 3F, the user may select, after inputting related registration information and before acquiring the first user information allocated by the server, another OTT application that may share the first user information. The foregoing is only a specific embodiment; in an actual application, the setting may be performed in multiple manners, and details are not described herein again. In this embodiment of the present invention, the interworking server receives, in multiple manners, second user information that is used by the user when the user accesses an OTT application. Optionally, for example, when the user accesses a second OTT application directly by using a client of the interworking server, the interworking server directly receives the second user information provided by a user client, and then performs authentication. For another example, when the user accesses an OTT application by using a server corresponding to the OTT application, the server corresponding to the OTT application sends, to the interworking server, the second user information that is sent by a user side, and the interworking server receives the second user information that is sent by the server corresponding to the OTT application, and then performs authentication. For still another example, when accessing an OTT application by using an OTT application client, the user is directly redirected to an OTT interworking server; then, the interworking server directly receives the second user information provided by a user client, and then performs authentication. In this embodiment of the present invention, the interworking server determines whether the first user information matches the second user information in multiple manners. For example, a manner of determining whether the first user information is consistent with the second user information may be used to determine whether the first user information matches the second user information; or a key encryption manner may be used to determine whether the first user information matches the second user information. In an actual application, the determining may be performed in many other manners, and details are not described herein again. In this embodiment of the present invention, the determining, by the interworking server, whether the first user information matches the second user information is actually authenticating and determining authenticity of the second user information according to the first user information; and whether the user is allowed to access the OTT application is further determined To determine, according to the second user information, whether the user is allowed to access an OTT application, the interworking server mainly performs the following operations: First, authenticity of a user identity is determined according to the acquired second user information, that is, an authenticity authentication function is performed. The interworking server authenticates user authenticity in multiple manners, such as a manner based on a user name/password or 3GPP (3rd Generation Partnership Project) GAA (generic authentication architecture). Because different OTT applications have different security requirements for user information of a user, the interworking server may perform security classification on the first user information of the user according to cases, so as to provide a more reliable platform to an OTT application. That is, to further improve security, in this embodiment of the present invention, after the authenticity of the user identity is determined, user access permission is further determined according to the second user information. The interworking server acquires user information in different manners. For example, for some OTT applications of higher security, checking is performed on some information when the user performs registration; therefore, the user information is relatively secure. However, for some other OTT applications, checking is not performed on information filled by the user during registration, therefore, security of the user information is relatively low. Therefore, the user access permission needs to be determined, where a manner of determining the access permission may be: determining whether a security level of the user information is greater than a preset security level threshold. In the embodiments of the present invention, three methods for pushing a message by a server corresponding to an OTT application are provided, and one of the three methods is specifically as follows: Referring to FIG. 4A, in an embodiment of the present invention, a first detailed flowchart of pushing a message by a server corresponding to an OTT application is as follows: Step 40: Receive a cross-OTT message push request that is sent by a server corresponding to a first OTT application, where the cross-OTT message push request is used by the server corresponding to the first OTT application to send a message to a terminal that does not access the first OTT application or does not register the first OTT application. Step 41: Select, according to stored and acquired user information for registering an OTT application, a cross-OTT information receiving user that receives the message sent by the server corresponding to the first OTT application, and send a message that is to be sent by the server corresponding to the first OTT application. In this embodiment of the present invention, in step 41, the message that is to be sent by the server corresponding to the first OTT application is sent to all selected cross-OTT information receiving users in multiple manners. For example, the received message that is sent by the server corresponding to the first OTT application is directly delivered to the cross-OTT information receiving user without using an OTT application server currently accessed by the cross-OTT information receiving user. The received message that is sent by the server corresponding to the first OTT application may also be sent to a server corresponding to a second OTT application that is accessed by the cross-OTT information receiving user, and then the message is sent to the cross-OTT information receiving user by the server corresponding to the second OTT application that is accessed by the cross-OTT information receiving user. Referring to FIG. 4B, in an embodiment of the present invention, a second detailed flowchart of pushing a message by a server corresponding to an OTT application is as follows: Step 400: Receive a cross-OTT message push request that is sent by a server corresponding to a first OTT application, where the cross-OTT message push request is used by the server corresponding to the first OTT application to send a message to a terminal that registers but does not access the first OTT application or does not register the first OTT application. Step 410: Select, according to stored and acquired user information for registering an OTT application, a cross-OTT information receiving user that receives the message sent by the server corresponding to the first OTT application, and send information about the selected cross-OTT information receiving user to the server corresponding to the first OTT application, so that the server corresponding to the first OTT application sends to-be-pushed information to the selected cross-OTT information receiving user. In the solution shown in FIG. 4B, the server corresponding to the first OTT application may not send a to-be-sent message to the interworking server, but first send the cross-OTT message push request to the interworking server, where the request is used by the server corresponding to the first OTT application to send the message to the terminal that registers but does not access the first OTT application or does not register the first OTT application. After receiving the request, the interworking server determines which users may receive the to-be-pushed message, considers these users as cross-OTT information receiving users, and knows a server currently accessed by these users. The interworking server is responsible for establishing a mutual trust connection between the server corresponding to the first OTT application and a server currently accessed by the cross OTT information receiving user. After the connection is established, the server corresponding to the first OTT application directly delivers the message that needs to be pushed and a list of receiving user names to the server currently accessed by the cross OTT information receiving user, and the server currently accessed by the cross OTT information receiving user pushes the message to a client of the cross-OTT information receiving user. Referring to FIG. 4C, in an embodiment of the present invention, a third detailed flowchart of pushing a message by a server corresponding to an OTT application is as follows: Step 4000: Acquire, according to stored and acquired user information for registering an OTT application, OTT information including user access information. Step 4100: Send the acquired OTT information to a server corresponding to a first OTT application, so that the server corresponding to the first OTT application determines a cross-OTT information receiving user to which a message is to be pushed, and pushes the to-be-pushed message to the cross-OTT information receiving user. In this embodiment, the OTT information further includes: intention information of a user, where the intention information of the user carries at least a type of information that the user intends to receive. In the foregoing three manners, before steps 40, 400, and 4000, the interworking server needs to acquire and store access information of each user (including whether the user is online, which server is currently accessed, and the like), where there are multiple specific manners for acquiring access information of the cross-OTT information receiving user. For example, manner (1): A user accesses a second OTT application by using a client corresponding to the second OTT application, where for a specific access manner, refer to steps 200 to 240. The interworking server may acquire access information of the user directly from an access process; or a server corresponding to the second OTT application notifies the interworking server of access information of the user after the user completes access to the second OTT application. For another example, manner (2): The cross-OTT information receiving user directly accesses the interworking server by using a client corresponding to the interworking server, so that the interworking server may directly acquire the access information from an access process. After acquiring the access information of the cross-OTT information receiving user, the interworking server may send the access information of the cross-OTT information receiving user to the server corresponding to the first OTT application, or may not send the access information of the cross-OTT information receiving user to the server corresponding to the first OTT application, where the access information includes at least a user account and a user online or offline state, and may further include a user nickname, an address and a domain name of the server corresponding to the first OTT application, and the like. Further, to prevent the user from receiving lots of junk information that the user is not interested in, corresponding to steps 41, 410, and 4100, specific screening and limitation need to be made on a range of the cross-OTT information receiving user selected by the server corresponding to the first OTT application. Specifically, possible manners are as follows: Manner 1: User online information that can be acquired by the interworking server may be limited to online information of all users that register account numbers on the server corresponding to the first OTT application. Manner 2: An interworking server provider (such as an operator) acquires intention information of a user. Content of the intention information may be whether allowing an online state of the user on an OTT application to be notified to a server corresponding to another OTT application that stores user information on the interworking server, or whether willing to receive a type of message (such as a game recommendation message or an advertisement message for fashion and shopping) or a call request sent by a server corresponding to another OTT application that stores user information on the interworking server, or whether willing to receive a message pushed by a server corresponding to a type of OTT application, or a specific OTT application name list. In addition, the interworking server may further acquire an attribute (such as a grade, a job type, or interests) of the user. The interworking server may screen, according to related information, an OTT application that may acquire online information of the user. It is worth pointing out that there are multiple manners for the user and the interworking server to acquire intention information of a cross-OTT information receiving user. For example, manner (a): A specific manner for acquiring the intention information may be that a corresponding option is provided on a registration page of a new user for the user to perform selection. When registering user information corresponding to a new OTT application, the user selects a type and a resource of a message that the user is willing to receive, and the like. The intention information may also be provided in a service manner. For example, the user subscribes a related service by means of a business office, a short message, or a manual telephone, and the interworking server stores the intention information of the user. For another example, manner (b):
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