A Socket combines an IP address with a port number, creating an endpoint for network communication. Think of it as an electrical outlet—once you establish a Socket, other programs can connect through it over the network.

For client applications, a single Socket instance suffices. However, server applications require two Socket objects: one for listening on a designated port, and additional instances created for each connected client to handle actual data exchange.

Server-Side Implementation

The following steps outline how to set up a listening Socket on the server:

// Initialize a stream-based TCP Socket
Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

// Configure the endpoint with IP and port
IPAddress localAddress = IPAddress.Parse("服务器IP地址");
IPEndPoint endpoint = new IPEndPoint(localAddress, 服务器端口);

// Bind the Socket to the network interface
listener.Bind(endpoint);

// Start listening with a connection queue
listener.Listen(backlogSize);

Once the Socket is bound and listening, spawn a dedicatde thread to accept incoming connections:

// Launch the monitoring thread
Thread monitorThread = new Thread(MonitorClients);
monitorThread.IsBackground = true;
monitorThread.Start();

// Continuous monitoring loop
private void MonitorClients()
{
    while (true)
    {
        // Create a new handler for each connecting client
        Socket clientHandler = listener.Accept();
        
        // Spawn a worker thread to process client data
        Thread workerThread = new Thread(ProcessClientData);
        workerThread.IsBackground = true;
        workerThread.Start(clientHandler);
    }
}

The worker thread receives messages from its assigned client:

private void ProcessClientData(object handler)
{
    Socket client = (Socket)handler;
    byte[] dataBuffer = new byte[bufferSize];
    
    while (client.Connected)
    {
        int bytesRead = client.Receive(dataBuffer);
        if (bytesRead > 0)
        {
            // Process received data
        }
    }
}

Client-Side Implementation

Clients establish connections with significantly less boilerplate code:

// Create a TCP Socket for the client
Socket sender = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

// Resolve the server address and port
IPAddress serverAddress = IPAddress.Parse("服务器IP");
IPEndPoint serverEndpoint = new IPEndPoint(serverAddress, 服务器端口);

// Connect to the server
sender.Connect(serverEndpoint);

// Send data to the server
byte[] messageBuffer = Encoding.UTF8.GetBytes("data to send");
sender.Send(messageBuffer);

The key distinction between client and server implementations lies in scope: servers must manage multiple concurrent connections through separate Socket instances, while clients typically miantain a single connection to transmit and receive data.