（C#:Socket）简单的服务端与客户端通信。

要求：
1.可以完成一对一的通信；
2.实现服务端对客户端一对多的选择发送；
3.可以实现服务端的群发功能；
4.可以实现客户端文件的发送；

要点：
服务器端：
第一步：用指定的端口号和服务器的ip建立一个EndPoint对像；
第二步：建立一个Socket对像；
第三步：用socket对像的Bind()方法绑定EndPoint；
第四步：用socket对像的Listen()方法开始监听；
第五步：接受到客户端的连接，用socket对像的Accept()方法创建新的socket对像用于和请求的客户端进行通信;
第六步：通信结束后一定记得关闭socket;

客户端：
第一步：用指定的端口号和服务器的ip建立一个EndPoint对像；
第二步：建立一个Socket对像；
第三步：用socket对像的Connect()方法以上面建立的EndPoint对像做为参数，向服务器发出连接请求；
第四步：如果连接成功，就用socket对像的Send()方法向服务器发送信息；
第五步：用socket对像的Receive()方法接受服务器发来的信息 ;
第六步：通信结束后一定记得关闭socket；

服务端代码如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.IO;

namespace Socket_ServerAndClient
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            TextBox.CheckForIllegalCrossThreadCalls = false;
        }

        Thread threadWatch = null;
        Socket socketWatch = null;

        /// <summary>
        /// 创建服务
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button1_Click(object sender, EventArgs e)
        {
            socketWatch = new Socket(AddressFamily.InterNetwork,SocketType.Stream,ProtocolType.Tcp);
            IPAddress address = IPAddress.Parse(txtIP.Text.Trim());
            IPEndPoint endpoint = new IPEndPoint(address,int.Parse(txtPort.Text.Trim()));
            socketWatch.Bind(endpoint);
            socketWatch.Listen(10);
            threadWatch = new Thread(WatchConnection);
            threadWatch.IsBackground = true;
            threadWatch.Start();
            ShowMsg("服务器监听成功......");
        }

        //Socket sokConnection = null;
        Dictionary<string, Socket> dict = new Dictionary<string, Socket>();
        Dictionary<string, Thread> dictThread = new Dictionary<string, Thread>();

        /// <summary>
        /// 监听客户端的请求方法
        /// </summary>
        /// <param name="obj"></param>
        private void WatchConnection(object obj)
        {
            while (true)
            {
                // 负责通信的套接字
                Socket sokConnection = socketWatch.Accept();
                lb_Online.Items.Add(sokConnection.RemoteEndPoint.ToString());
                dict.Add(sokConnection.RemoteEndPoint.ToString(),sokConnection);

                //创建通信线程
                ParameterizedThreadStart pts = new ParameterizedThreadStart(RecMsg);// 委托
                Thread thr = new Thread(pts);
                thr.IsBackground = true;
                thr.Start(sokConnection);
                dictThread.Add(sokConnection.RemoteEndPoint.ToString(),thr);

                ShowMsg("客户端连接成功......"+sokConnection.RemoteEndPoint.ToString());
            }
        }

        /// <summary>
        /// 服务端负责监听客户端发送消息的方法
        /// </summary>
        void RecMsg(object socketClient)
        {
            Socket socketClients = socketClient as Socket;
            while (true)
            {
                byte[] arrMsgRec = new byte[1024 * 1024 * 2];

                int length = -1;
                try
                {
                    length = socketClients.Receive(arrMsgRec);
                }
                catch (SocketException ex)
                {
                    ShowMsg("异常：" + ex.Message);
                    // 从 通信套接字 集合中删除被中断连接的套接字对象
                    dict.Remove(socketClients.RemoteEndPoint.ToString());
                    // 从 通信线程 集合中删除被中断连接的套接字对象
                    dictThread.Remove(socketClients.RemoteEndPoint.ToString());
                    // 从 列表 中移除 IP&Port
                    lb_Online.Items.Remove(socketClients.RemoteEndPoint.ToString());
                    break;
                }
                catch (Exception ex)
                {
                    ShowMsg("异常：" + ex.Message);
                    break;
                }
                // 判断第一个发送过来的数据如果是1，则代表发送过来的是文本数据
                if (arrMsgRec[0] == 0)
                {
                    string strMsgRec = System.Text.Encoding.UTF8.GetString(arrMsgRec, 1, length-1);
                    ShowMsg(strMsgRec);
                }
                // 若是1则发送过来的是文件数据（文档，图片，视频等。。。）
                else if(arrMsgRec[0] == 1)
                {
                    // 保存文件选择框对象
                    SaveFileDialog sfd = new SaveFileDialog();
                    // 选择文件路径
                    if (sfd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
                    {
                        // 获得保存文件的路径
                        string fileSavePath = sfd.FileName;
                        // 创建文件流，然后让文件流根据路径创建一个文件
                        using (FileStream fs = new FileStream(fileSavePath, FileMode.Create))
                        {
                            fs.Write(arrMsgRec, 1, length - 1);
                            ShowMsg("文件保存成功："+fileSavePath);
                        }
                    }
                }
            }
        }

        private void ShowMsg(string p)
        {
            txtMsg.AppendText(p+"\r\n");
        }

        /// <summary>
        /// 发送消息
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Send_Click_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(lb_Online.Text))
            {
                MessageBox.Show("请选择发送的好友！！！");
            }
            else
            {
                string strMsg = tb_Msg_Send.Text.Trim();
                byte[] arrMsg = System.Text.Encoding.UTF8.GetBytes(strMsg);
                string strClientKey = lb_Online.Text;
                try
                {
                    dict[strClientKey].Send(arrMsg);
                    ShowMsg("发送了数据出去："+strMsg);
                }
                catch (SocketException ex)
                {
                    ShowMsg("发送时异常：" + ex.Message);
                }
                catch(Exception ex)
                {
                    ShowMsg("发送时异常：" + ex.Message);
                }
                // sokConnection.Send(arrMsg);
                ShowMsg("发送了数据出去："+strMsg);
            }
        }

        /// <summary>
        /// 群发消息
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void SendToAll_Click(object sender, EventArgs e)
        {
            string strMsg = txtMsg.Text.Trim();
            byte[] arrMsg = System.Text.Encoding.UTF8.GetBytes(strMsg);
            foreach (Socket item in dict.Values)
            {
                item.Send(arrMsg);
            }
            ShowMsg("群发完毕！！！:）");
        }
    }
}

　　

客户端代码如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.IO;

namespace Socket_Client
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            TextBox.CheckForIllegalCrossThreadCalls = false;
        }

        Thread threadRec = null;
        Socket socketClient = null;

        private void btn_Connect_Click(object sender, EventArgs e)
        {
            IPAddress address = IPAddress.Parse(tb_IP.Text.Trim());
            IPEndPoint endport = new IPEndPoint(address,int.Parse(tb_Port.Text.Trim()));
            socketClient = new Socket(AddressFamily.InterNetwork,SocketType.Stream,ProtocolType.Tcp);
            socketClient.Connect(endport);

            threadRec = new Thread(RecMsg);
            threadRec.IsBackground = true;
            threadRec.Start();
        }

        void RecMsg()
        {
            while (true)
            {
                byte[] arrMsgRec = new byte[1024*1024*2];
                int length = socketClient.Receive(arrMsgRec);
                string strMsgRec = System.Text.Encoding.UTF8.GetString(arrMsgRec,0,length);
                ShowMsg(strMsgRec);
            }
        }

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

        private void btnSendMsg_Click(object sender, EventArgs e)
        {
            string strMsg = txtMsgSend.Text.Trim();
            byte[] arrMsg = System.Text.Encoding.UTF8.GetBytes(strMsg);
            byte[] arrMsgSend = new byte[arrMsg.Length];
            // 添加标识位，0代表发送的是文字
            arrMsgSend[0] = 0;
            Buffer.BlockCopy(arrMsg, 0, arrMsgSend, 1, arrMsg.Length);
            socketClient.Send(arrMsg);
            ShowMsg("I say:"+strMsg);
        }

        /// <summary>
        /// 选择文件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btChoseFile_Click(object sender, EventArgs e)
        {
            OpenFileDialog ofd = new OpenFileDialog();
            if (ofd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
            {
                txtFilePath.Text = ofd.FileName;
            }
        }

        /// <summary>
        /// 发送文件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btSendFile_Click(object sender, EventArgs e)
        {
            using (FileStream fs = new FileStream())
            {
                byte[] arrFile = new byte[1024*1024*2];
                int length = fs.Read(arrFile, 0, arrFile.Length);
                byte[] arrFileSend = new byte[length+1];
                arrFileSend[0] = 1;// 代表文件数据
                // 将数组 arrFile 里的数据从第零个数据拷贝到 数组 arrFileSend 里面，从第1个开始，拷贝length个数据
                Buffer.BlockCopy(arrFile, 0, arrFileSend, 1, length);
                socketClient.Send(arrFileSend);
            }
        }
    }
}

程序运行截图：