TCP客户端模拟链接websocket服务端

因一些特殊原因研究了下TCP模拟链接websocket。原理上可以连接但具体怎么连接怎么操作就不知道了，需要研究下，以下是个人研究的方案。

用线上和本地地址来做例子：

线上wss地址：wss://server.cs.com/cs/vido/1

本地地址ws://127.0.0.1/cs/vido/1

如果用本地地址来模拟websocket，需要遵从websocket协议。WebSocket协议需要通过已建立的TCP连接来传输数据。具体实现上是通过http协议建立通道，然后在此基础上用真正的WebSocket协议进行通信，所以WebSocket协议和http协议是有一定的交叉关系的。

在tcp与websocket消息交互之前需要先和websocket建立握手关系：

GET /cs/vido HTTP/1.1
Host: server.cs.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: x3JJHMbDL1EzLkh9GBhXDw==
Sec-WebSocket-Version: 13

Get输出的是ws后面的子路径地址

Host输出的是域名地址

upgrade、Connection输出的是要升级到websocket通讯

Sec-WebSocket-Key输出的是Base64 encode 的值，这个是随机生成的。

Sec-WebSocket-Version输出的是websocket的版本，默认必须是13

websocket服务器收到客户端消息后会返回验证消息；

HTTP/1.1 101 
Connection: upgrade
Vary: Access-Control-Request-Method
Vary: Access-Control-Request-Headers
Upgrade: websocket
Sec-WebSocket-Accept: sT7MD7zMs7k3yPTFV6JvttwPwoE=

客户端接收到服务端发送的新的Sec-WebSocket-Accept参数后，使用原来的随机密钥和新的Sec-WebSocket-Accept参数共同生成一个新的Sec-WebSocket-Key参数，用于加密数据传输。
客户端将新的Sec-WebSocket-Key参数发送给服务端，服务端接收到后，使用该参数加密数据传输，收到此消息后是代表已经和websocket建立了联系。

这块要注意下，如果是用本地地址去测试没问题，但用正式地址去测试就会被提示需要ssl加密。

使用ssl加密代码如下：

 _tcpClient = new TcpClient(host, port);_networkStream = _tcpClient.GetStream();// 创建SslStreamSslStream sslStream = new SslStream(_networkStream, false, new RemoteCertificateValidationCallback(ValidateServerCertificate), null);// 验证服务器证书sslStream.AuthenticateAsClient(host);// 验证服务器证书的回调函数public static bool ValidateServerCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors){if (sslPolicyErrors == SslPolicyErrors.None)return true;Console.WriteLine("Certificate error: {0}", sslPolicyErrors);return false;}

用了ssl加密和没用ssl加密的获取的消息也是不一样的，如果用了ssl加密后就要用sslStream来接收消息或者发送消息否则会乱码。没有用ssl加密那就用_networkStream来接收或者发送消息。

整体代码如下：

public class WebSocketClient2{private TcpClient _tcpClient;private NetworkStream _networkStream;public void ConnectToWebSocket(string host, int port, string resource){_tcpClient = new TcpClient(host, port);_networkStream = _tcpClient.GetStream();// 创建SslStreamSslStream sslStream = new SslStream(_networkStream, false, new RemoteCertificateValidationCallback(ValidateServerCertificate), null);// 验证服务器证书sslStream.AuthenticateAsClient(host);// 构建WebSocket握手消息string key = Convert.ToBase64String(Encoding.UTF8.GetBytes(Guid.NewGuid().ToString()));string handshakeMessage = $"GET {resource} HTTP/1.1\r\n" +$"Host:{host}\r\n" +"Upgrade: websocket\r\n" +"Connection: Upgrade\r\n" +$"Sec-WebSocket-Key: {key}\r\n" +"Sec-WebSocket-Version: 13\r\n" +"\r\n";// 发送握手消息byte[] handshakeBuffer = Encoding.UTF8.GetBytes(handshakeMessage);//_networkStream.Write(handshakeBuffer, 0, handshakeBuffer.Length);sslStream.Write(handshakeBuffer, 0, handshakeBuffer.Length);// 接收服务器响应并验证byte[] buffer = new byte[1024];//int bytesRead = _networkStream.Read(buffer, 0, buffer.Length);int bytesRead = sslStream.Read(buffer, 0, buffer.Length);string response = Encoding.UTF8.GetString(buffer, 0, bytesRead);Console.WriteLine(response);// 验证服务器响应的Sec-WebSocket-Acceptstring expectedResponse = Convert.ToBase64String(SHA1.Create().ComputeHash(Encoding.ASCII.GetBytes(key + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11")));if (response.Contains($"Sec-WebSocket-Accept: {expectedResponse}")){Console.WriteLine("WebSocket handshake successful.");}else{Console.WriteLine("WebSocket handshake failed.");}byte[] buffer2 = new byte[1024];int bytesRead2;while ((bytesRead2 = sslStream.Read(buffer2, 0, buffer2.Length)) > 0){string message = Encoding.UTF8.GetString(buffer2, 0, bytesRead2);// 解析WebSocket消息// ...Console.WriteLine($"Received message: {message}");}}// 验证服务器证书的回调函数public static bool ValidateServerCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors){if (sslPolicyErrors == SslPolicyErrors.None)return true;Console.WriteLine("Certificate error: {0}", sslPolicyErrors);return false;}}//代码实现调用WebSocketClient2 client = new WebSocketClient2();client.ConnectToWebSocket("server.cs.com.cn", 443, "/cs/vido/1");//测试环境ws端口号默认是80，wss默认端口号是443