Socket 网络编程实战：C# 服务端与客户端通信实现

上述代码仅支持单客户端连接，存在局限性。需完善为循环接收连接。

服务端代码 2：循环接收客户端连接

void Listen(object o)
{
    Socket socket = o as Socket;
    while (true)
    {
        Socket connSocket = socket.Accept();
        ShowMsg(connSocket.RemoteEndPoint.ToString());
        
        byte[] buffer = new byte[1024 * 1023];
        int num = connSocket.Receive(buffer);
        string str = Encoding.UTF8.GetString(buffer, 0, num);
        ShowMsg(str);
    }
}

服务端代码 3：循环接收消息

void Listen(object o)
{
    Socket socket = o as Socket;
    while (true)
    {
        Socket connSocket = socket.Accept();
        ShowMsg(connSocket.RemoteEndPoint.ToString());
        
        while (true)
        {
            byte[] buffer = new byte[1024 * 1023];
            int num = connSocket.Receive(buffer);
            string str = Encoding.UTF8.GetString(buffer, 0, num);
            ShowMsg(str);
        }
    }
}

服务端代码 4：循环多个客户端并接收信息

void Listen(object o)
{
    Socket socket = o as Socket;
    while (true)
    {
        Socket connSocket = socket.Accept();
        ShowMsg(connSocket.RemoteEndPoint.ToString());
        
        Thread th = new Thread(RecMsg);
        th.IsBackground = true;
        th.Start(connSocket);
    }
}

void RecMsg(object o)
{
    Socket connSocket = o as Socket;
    while (true)
    {
        byte[] buffer = new byte[1024 * 1024];
        int num = connSocket.Receive(buffer);
        string str = Encoding.UTF8.GetString(buffer, 0, num);
        ShowMsg(connSocket.RemoteEndPoint.ToString() + ":" + str);
    }
}

服务端代码 5：限制客户端连接数

int count = 0;
void Listen(object o)
{
    Socket socket = o as Socket;
    while (count < 1000)
    {
        Socket connSocket = socket.Accept();
        ShowMsg(connSocket.RemoteEndPoint.ToString());
        
        Thread th = new Thread(RecMsg);
        th.IsBackground = true;
        th.Start(connSocket);
        count++;
    }
}

服务端代码 6：处理客户端断开（空字节）

void RecMsg(object o)
{
    Socket connSocket = o as Socket;
    while (true)
    {
        byte[] buffer = new byte[1024 * 1024];
        int num = connSocket.Receive(buffer);
        
        if (num == 0)
        {
            ShowMsg(connSocket.RemoteEndPoint.ToString() + ":退出");
            connSocket.Shutdown(SocketShutdown.Receive);
            connSocket.Close();
            break;
        }
        
        string str = Encoding.UTF8.GetString(buffer, 0, num);
        ShowMsg(connSocket.RemoteEndPoint.ToString() + ":" + str);
    }
}

客户端代码 1：连接与服务端通信

public Form1()
{
    InitializeComponent();
    Control.CheckForIllegalCrossThreadCalls = false;
}

Socket socket;

private void btnConnect_Click(object sender, EventArgs e)
{
    IPAddress ip = IPAddress.Parse(txtIP.Text);
    IPEndPoint point = new IPEndPoint(ip, int.Parse(txtPortNumber.Text));
    socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
    try
    {
        socket.Connect(point);
        ShowMsg("连接成功");
    }
    catch (Exception ex)
    {
        ShowMsg(ex.Message);
    }
}

void ShowMsg(string msg)
{
    txtShowMessage.AppendText(msg + "\r\n");
}

private void btnSendMessage_Click(object sender, EventArgs e)
{
    if (socket != null)
    {
        byte[] buffer = Encoding.UTF8.GetBytes(txtInputMessage.Text);
        socket.Send(buffer);
    }
    else
    {
        MessageBox.Show("请先连接");
    }
}

服务端代码 7：处理异常断开

void RecMsg(object o)
{
    Socket connSocket = o as Socket;
    while (true)
    {
        byte[] buffer = new byte[1024 * 1024];
        int num = -1;
        try
        {
            num = connSocket.Receive(buffer);
            if (num == 0)
            {
                ShowMsg(connSocket.RemoteEndPoint.ToString() + ":退出");
                connSocket.Shutdown(SocketShutdown.Receive);
                connSocket.Close();
                break;
            }
            string str = Encoding.UTF8.GetString(buffer, 0, num);
            ShowMsg(connSocket.RemoteEndPoint.ToString() + ":" + str);
        }
        catch (Exception ex)
        {
            ShowMsg(ex.Message);
            break;
        }
    }
}

服务端代码 8：服务端发送消息

private void btnSendMessage_Click(object sender, EventArgs e)
{
    if (connSocket != null)
    {
        byte[] buffer = Encoding.UTF8.GetBytes(txtInputMessage.Text);
        try
        {
            connSocket.Send(buffer);
        }
        catch (Exception ex)
        {
            ShowMsg(ex.Message);
        }
    }
}

客户端代码 2：接收服务端消息

void RecMsg()
{
    while (true)
    {
        byte[] buffer = new byte[1024 * 1024];
        try
        {
            int num = socket.Receive(buffer);
            string str = Encoding.UTF8.GetString(buffer, 0, num);
            ShowMsg(str);
        }
        catch (Exception ex)
        {
            ShowMsg(ex.Message);
            break;
        }
    }
}

Thread th = new Thread(RecMsg);
th.IsBackground = true;
th.Start();

服务端代码 9：指定客户端发送消息

Dictionary<string, Socket> dic = new Dictionary<string, Socket>();
int count = 0;

void Listen(object o)
{
    Socket socket = o as Socket;
    while (count < 100)
    {
        count++;
        Socket connSocket = socket.Accept();
        ShowMsg(connSocket.RemoteEndPoint.ToString());
        
        string ipport = connSocket.RemoteEndPoint.ToString();
        cboUser.Items.Add(ipport);
        dic.Add(ipport, connSocket);
        
        Thread th = new Thread(RecMsg);
        th.IsBackground = true;
        th.Start(connSocket);
    }
}

private void btnSendMessage_Click(object sender, EventArgs e)
{
    string ipport = cboUser.Text;
    if (!string.IsNullOrEmpty(ipport))
    {
        byte[] buffer = Encoding.UTF8.GetBytes(txtInputMessage.Text);
        try
        {
            Socket connSocket = dic[ipport];
            connSocket.Send(buffer);
        }
        catch (Exception ex)
        {
            ShowMsg(ex.Message);
        }
    }
    else
    {
        MessageBox.Show("请选择客户端");
    }
}