C#利用服务器实现客户端之间通信

这两天在学习C#，C#高级编程真的是厚厚的一本书QAQ。

昨天看了一下里面的通信部分(其实还没怎么看),看了网上一些人的博客，自己在他们的博客基础上写了一个通信。

先来讲述下我自己对于整个Socket通信过程的理解，毕竟初学，说错见谅，知道错了会改正~

首先在服务端新建一个serverSocket，对其进行初始化（一般包含AddressFamily:IP地址类型，SocketType:Socket传输数据方式，ProtoType:传输协议）;

接着我们要设置server端要绑定的IP:port;然后开始监听，并设置最多同时监听多少个Client.

这时，服务端就在等待状态，直到某一个Client连接到这个ip:port上，这时serverSocket.Accept()工作，获得这个连接。（此时的连接是有地址信息的哦！记得保存）

获得连接之后，server就可以和这个Client进行通信了,当加入第二个Client（我们称其为ClientB）时，Server接收到ClientB的消息，可以将这个消息转发给前一个Client（我们称其为ClientA），当受到ClientA的消息，也可以转发给ClientB。这样就实现了Clients之间的通信了。（重点在保存连接信息！！）

那么现在贴上代码讲解：

Server端代码

namespace SocketServer
{
    class Program
    {
        private static byte[] result = new byte[1024];
      
        static Socket serverSocket;
        private static string client;
        private static Socket clientSocket;
        //我这里存了两个Client，因为自己电脑开了两个Client，不会有多的
        //理论上应该开一个Socket[]来保存信息，最好用一个二元组将client的信息和连接绑定起来
        //这样就可以实现断开连接后下次登陆还是可以识别是这个Client
        private static Socket clientSocketA=null;
        private static Socket clientSocketB=null;
        
        static void Main(string[] args)
        {
            Program.SetPort(8885);
        }
        private static void SetPort(int port)
        {
            IPAddress ip = IPAddress.Parse("127.0.0.1");//set ip
            serverSocket = new Socket(AddressFamily.InterNetwork,
                SocketType.Stream, ProtocolType.Tcp);//initialize
            serverSocket.Bind(new IPEndPoint(ip, port));//bind
            serverSocket.Listen(10);
            //进入监听状态
            Console.WriteLine("监听{0}成功", serverSocket.LocalEndPoint.ToString());
            //开启一个线程来监听客户端连接
            Thread myThread = new Thread(ListenClientConnect);
            myThread.Start();
            Console.ReadLine();

        }
        /// <summary>
        /// 监听客户端连接
        /// </summary>
        private static void ListenClientConnect()
        {
            while (true)
            {
                //Client连接上后 得到这个连接
                clientSocket = serverSocket.Accept();

                //这里我因为只有两个Client，所以就简单写了
                if (clientSocketA == null)
                {
                    clientSocketA = clientSocket;
                }
                else if (clientSocketB == null)
                {
                    clientSocketB = clientSocket;
                }
                else
                {
                    //当其中一个断开了，又重新连接时，需要再次保存连接
                    if (clientSocketB.IsBound)
                    {
                        clientSocketA = clientSocketB;
                        clientSocketB = clientSocket;
                    }
                    else
                    {
                        clientSocketB = clientSocketA;
                        clientSocketA = clientSocket;
                    }
                    
                }
                clientSocket.Send(Encoding.ASCII.GetBytes("say hello"));
                //开个线程接收Client信息
                Thread receivedThread = new Thread(ReceiveMessage);
                receivedThread.Start(clientSocket);

            }
        }
     
        private static void ReceiveMessage(object clientSocket)
        {
            Socket myClientSocket = (Socket) clientSocket;
            
            while (true)
            {
                try
                {
                    int revceiveNumber = myClientSocket.Receive(result);
                    //Console.WriteLine("接受客户端{0}消息{1}", myClientSocket.RemoteEndPoint.ToString()
                    //    , Encoding.ASCII.GetString(result, 0, revceiveNumber));
                    Console.WriteLine(Encoding.ASCII.GetString(result, 0, revceiveNumber));
                    if (myClientSocket == clientSocketA)
                    {
                        Console.WriteLine("receive from A");
                        if (clientSocketB!=null&&clientSocketB.IsBound)
                        {
                            Console.WriteLine("a IS BOUND");
                            clientSocketB.Send(result, 0, revceiveNumber, SocketFlags.None);
                        }
                        else
                        {
                            myClientSocket.Send(Encoding.ASCII.GetBytes("the people is not online! Send Failed!"));
                            Console.WriteLine("对方不在线上，发送失败！");
                        }
                    }
                    else
                    {
                        Console.WriteLine("receive from B");
                        if (clientSocketA != null && clientSocketA.IsBound)
                        {
                            Console.WriteLine("a IS BOUND");
                            clientSocketA.Send(result, 0, revceiveNumber, SocketFlags.None);
                        }   
                        else
                        {
                            myClientSocket.Send(Encoding.ASCII.GetBytes("the people is not online! Send Failed!"));
                            Console.WriteLine("对方不在线上，发送失败！");
                        }

                    }
                    
                }
                catch(Exception ex)
                {
                    Console.WriteLine(ex.Message);
                    myClientSocket.Shutdown(SocketShutdown.Both);
                    myClientSocket.Close();
                    break;

                }
            }

        }
    }
}

Client端代码(因为都差不多 就只贴一个了)

namespace SocketClient
{
    class Program
    {
        private static byte[] result = new byte[1024];
        private static Socket clientSocket;
        private static void ListenServer()
        {
            while (true)
            {
                result = new byte[1024];
                int receiveLength = clientSocket.Receive(result);
                
                Console.WriteLine("{0}", Encoding.ASCII.GetString(result, 0, receiveLength));
            }
           
        }
        static void Main(string[] args)
        {

            IPAddress ip = IPAddress.Parse("127.0.0.1");
            clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            try
            {
                clientSocket.Connect(ip, 8885);
                Console.WriteLine("连接成功！");

            }
            catch (Exception e)
            {
                Console.WriteLine("连接失败！");
                return;
            }
            Thread threadRead = new Thread(ListenServer);
            threadRead.Start();
           

            while(true)
            {
                try
                {
                    Thread.Sleep(1000);
                    string sendMessage = Console.ReadLine();
                    clientSocket.Send(Encoding.ASCII.GetBytes("Sylvia:"+sendMessage));
                    
                }
                catch (Exception ex)
                {
                    clientSocket.Shutdown(SocketShutdown.Both);
                    clientSocket.Close();
                    break;
                }

            }
            Console.WriteLine("发送完毕 按回车退出");
            Console.ReadKey();
        }
    }
}

写的时候要特别注意一下Send信息的时候，注意byte[]的传输大小，很容易变成byte[]数组的大小而不是内容的大小。

这个大家就自己尝试吧