Im trying to connect to a commetd server via websocket client. I used exactly the code from an [official cometd demo on github](https://github.com/cometd/cometd/blob/master/cometd-demo/src/test/java/org/cometd/demo/Demo.java) without modifications and try to connect to <http://localhost:8080/cometd/test>

.. but as soon as my client tries to do the websocket upgrade http request I get a response with "HTTP/1.1 400 Unknown Bayeux Transport"
Any ideas?

I tried it with SSL and without it, the latter obviosly to reduce potential error sources. In both cases I get the same error.

Here is my pom, in case I forgot some important websocket related dependencies

```
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
                      http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>de.verlinkied</groupId>
    <artifactId>bayeux-server</artifactId>
    <version>1.0</version>

    <properties>
        <jetty.version>9.2.22.v20170606</jetty.version>
        <cometd.version>3.1.3</cometd.version>
        <slf4j.version>1.7.25</slf4j.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.eclipse.jetty.websocket</groupId>
            <artifactId>websocket-api</artifactId>
            <version>${jetty.version}</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.jetty</groupId>
            <artifactId>jetty-server</artifactId>
            <version>${jetty.version}</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.jetty</groupId>
            <artifactId>jetty-servlet</artifactId>
            <version>${jetty.version}</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.jetty</groupId>
            <artifactId>jetty-jmx</artifactId>
            <version>${jetty.version}</version>
        </dependency>

        <dependency>
            <groupId>org.eclipse.jetty.websocket</groupId>
            <artifactId>javax-websocket-server-impl</artifactId>
            <version>${jetty.version}</version>
        </dependency>

        <dependency>
            <groupId>org.cometd.java</groupId>
            <artifactId>cometd-java-server</artifactId>
            <version>${cometd.version}</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${slf4j.version}</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>${slf4j.version}</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <configuration>
                    <mainClass>de.verlinked.BayeuxServerTest</mainClass>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

```

mvn dependency:tree yields the following

```
[INFO] ------------------------------------------------------------------------
[INFO] Building bayeux-server 1.0
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ bayeux-server ---
[INFO] de.verlinkied:bayeux-server:jar:1.0
[INFO] +- org.eclipse.jetty.websocket:websocket-api:jar:9.2.22.v20170606:compile
[INFO] +- org.eclipse.jetty:jetty-server:jar:9.2.22.v20170606:compile
[INFO] |  +- javax.servlet:javax.servlet-api:jar:3.1.0:compile
[INFO] |  +- org.eclipse.jetty:jetty-http:jar:9.2.22.v20170606:compile
[INFO] |  \- org.eclipse.jetty:jetty-io:jar:9.2.22.v20170606:compile
[INFO] +- org.eclipse.jetty:jetty-servlet:jar:9.2.22.v20170606:compile
[INFO] |  \- org.eclipse.jetty:jetty-security:jar:9.2.22.v20170606:compile
[INFO] +- org.eclipse.jetty:jetty-jmx:jar:9.2.22.v20170606:compile
[INFO] |  \- org.eclipse.jetty:jetty-util:jar:9.2.22.v20170606:compile
[INFO] +- org.eclipse.jetty.websocket:javax-websocket-server-impl:jar:9.2.22.v20170606:compile
[INFO] |  +- org.eclipse.jetty:jetty-annotations:jar:9.2.22.v20170606:compile
[INFO] |  |  +- org.eclipse.jetty:jetty-plus:jar:9.2.22.v20170606:compile
[INFO] |  |  |  \- org.eclipse.jetty:jetty-jndi:jar:9.2.22.v20170606:compile
[INFO] |  |  +- org.eclipse.jetty:jetty-webapp:jar:9.2.22.v20170606:compile
[INFO] |  |  |  \- org.eclipse.jetty:jetty-xml:jar:9.2.22.v20170606:compile
[INFO] |  |  +- javax.annotation:javax.annotation-api:jar:1.2:compile
[INFO] |  |  +- org.ow2.asm:asm:jar:5.0.1:compile
[INFO] |  |  \- org.ow2.asm:asm-commons:jar:5.0.1:compile
[INFO] |  |     \- org.ow2.asm:asm-tree:jar:5.0.1:compile
[INFO] |  +- org.eclipse.jetty.websocket:javax-websocket-client-impl:jar:9.2.22.v20170606:compile
[INFO] |  |  \- org.eclipse.jetty.websocket:websocket-client:jar:9.2.22.v20170606:compile
[INFO] |  +- org.eclipse.jetty.websocket:websocket-server:jar:9.2.22.v20170606:compile
[INFO] |  |  +- org.eclipse.jetty.websocket:websocket-common:jar:9.2.22.v20170606:compile
[INFO] |  |  \- org.eclipse.jetty.websocket:websocket-servlet:jar:9.2.22.v20170606:compile
[INFO] |  \- javax.websocket:javax.websocket-api:jar:1.0:compile
[INFO] +- org.cometd.java:cometd-java-server:jar:3.1.3:compile
[INFO] |  +- org.cometd.java:bayeux-api:jar:3.1.3:compile
[INFO] |  \- org.cometd.java:cometd-java-common:jar:3.1.3:compile
[INFO] |     \- org.eclipse.jetty:jetty-util-ajax:jar:9.2.22.v20170606:compile
[INFO] +- org.slf4j:slf4j-api:jar:1.7.25:compile
[INFO] \- org.slf4j:slf4j-log4j12:jar:1.7.25:compile
[INFO]    \- log4j:log4j:jar:1.2.17:compile
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------

```

The jetty log shows the following 

```
3411 [qtp1080615555-20] DEBUG org.eclipse.jetty.server.HttpChannel  - HttpChannelOverHttp@31f5a8ff{r=1,c=false,a=IDLE,uri=/cometd/test} messageComplete
3411 [qtp1080615555-20] DEBUG org.eclipse.jetty.server.HttpInput  - HttpInputOverHTTP@6f0992d0 EOF
3411 [qtp1080615555-20] DEBUG org.eclipse.jetty.server.HttpChannel  - HttpChannelOverHttp@31f5a8ff{r=1,c=false,a=IDLE,uri=/cometd/test} handle enter
3412 [qtp1080615555-20 - /cometd/test] DEBUG org.eclipse.jetty.server.HttpChannelState  - HttpChannelState@738a2171{s=IDLE i=true a=null} handling IDLE
3412 [qtp1080615555-20 - /cometd/test] DEBUG org.eclipse.jetty.server.HttpChannel  - HttpChannelOverHttp@31f5a8ff{r=1,c=false,a=DISPATCHED,uri=/cometd/test} action REQUEST_DISPATCH
3412 [qtp1080615555-20 - /cometd/test] DEBUG org.eclipse.jetty.server.Server  - REQUEST GET /cometd/test on HttpChannelOverHttp@31f5a8ff{r=1,c=false,a=DISPATCHED,uri=/cometd/test}
3412 [qtp1080615555-20 - /cometd/test] DEBUG org.eclipse.jetty.server.handler.ContextHandler  - scope null||/cometd/test @ o.e.j.s.ServletContextHandler@35fdf572{/,null,AVAILABLE}
3413 [qtp1080615555-20 - /cometd/test] DEBUG org.eclipse.jetty.server.handler.ContextHandler  - context=||/cometd/test @ o.e.j.s.ServletContextHandler@35fdf572{/,null,AVAILABLE}
3413 [qtp1080615555-20 - /cometd/test] DEBUG org.eclipse.jetty.servlet.ServletHandler  - servlet |/cometd|/test -> org.cometd.server.CometDServlet-629a2d4a@4553b89a==org.cometd.server.CometDServlet,1,true
3413 [qtp1080615555-20 - /cometd/test] DEBUG org.eclipse.jetty.servlet.ServletHandler  - chain=Jetty_WebSocketUpgradeFilter->org.cometd.server.CometDServlet-629a2d4a@4553b89a==org.cometd.server.CometDServlet,1,true
3414 [qtp1080615555-20 - /cometd/test] DEBUG org.eclipse.jetty.servlet.ServletHandler  - call filter Jetty_WebSocketUpgradeFilter
3416 [qtp1080615555-20 - /cometd/test] DEBUG org.eclipse.jetty.servlet.ServletHandler  - call servlet org.cometd.server.CometDServlet-629a2d4a@4553b89a==org.cometd.server.CometDServlet,1,true
3418 [qtp1080615555-20 - /cometd/test] DEBUG org.eclipse.jetty.server.HttpConnection  - org.eclipse.jetty.server.HttpConnection$SendCallback@62e6f50[PROCESSING][i=ResponseInfo{HTTP/1.1 400 Unknown Bayeux Transport,304,false},cb=org.eclipse.jetty.server.HttpChannel$CommitCallback@6892f8b1] generate: NEED_HEADER (null,[p=0,l=304,c=2048,r=304],true)@START

```

Where you can see that some Jetty\_WebSocketUpgradeFilter is called, which makes me think that the websocket dependency is present but still something goes wrong.