text: // Copyright 2018 The Outline Authors
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //      http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  #ifndef ShadowsocksConnectivity_h
  #define ShadowsocksConnectivity_h
  
  #import <Foundation/Foundation.h>
  #import "PacketTunnelProvider.h"
  
  /**
   * Non-thread-safe class to perform Shadowsocks connectivity checks.
   */
  @interface ShadowsocksConnectivity : NSObject
  
  /**
   * Initializes the object with a local Shadowsocks port, |shadowsocksPort|.
   */
  - (id)initWithPort:(uint16_t)shadowsocksPort;
  
  /**
   * Verifies that the server has enabled UDP forwarding. Performs an end-to-end test by sending
   * a DNS request through the proxy. This method is a superset of |checkServerCredentials|, as its
   * success implies that the server credentials are valid.
   */
  - (void)isUdpForwardingEnabled:(void (^)(BOOL))completion;
  
  /**
   * Verifies that the server credentials are valid. Performs an end-to-end authentication test
   * by issuing an HTTP HEAD request to a target domain through the proxy.
   */
  - (void)checkServerCredentials:(void (^)(BOOL))completion;
  
  /**
   * Checks that the server is reachable on |host| and |port|.
   */
  - (void)isReachable:(NSString *)host port:(uint16_t)port completion:(void (^)(BOOL))completion;
  
  @end
  
  #endif /* ShadowsocksConnectivity_h */
  