Question

C# 客户端与服务器通信问题

当客户端发送广播，服务器监听，建立连接，发送数据；连接建立后，服务器停止发送广播，开始发送数据，且隔几秒发送一次，若数据发送失败，就断开连接，重新发送广播。
具体怎么实现？

Answer 1

客户端：
static void Main(string[] args)
{
//创建一个Socket
var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
//连接到指定服务器的指定端口
socket.Connect("localhost", 4530);
Console.WriteLine("connect to the server");
//实现接受消息的方法
socket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(ReceiveMessage), socket);
//接受用户输入，将消息发送给服务器端
while(true)
{
var message = "Message from client : " + Console.ReadLine();
var outputBuffer = Encoding.Unicode.GetBytes(message);
socket.BeginSend(outputBuffer, 0, outputBuffer.Length, SocketFlags.None, null, null);
}
}

static byte[] buffer = new byte[1024];
public static void ReceiveMessage(IAsyncResult ar)
{
try
{
var socket = ar.AsyncState as Socket;
var length = socket.EndReceive(ar);
//读取出来消息内容
var message = Encoding.Unicode.GetString(buffer, 0, length);
//显示消息
Console.WriteLine(message);
//接收下一个消息(因为这是一个递归的调用，所以这样就可以一直接收消息了）
socket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(ReceiveMessage), socket);
}
catch(Exception ex)
{
Console.WriteLine(ex.Message);
}
}

服务器端：
static void Main(string[] args)
{
//创建一个新的Socket,这里我们使用最常用的基于TCP的Stream Socket（流式套接字）
var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
//将该socket绑定到主机上面的某个端口
socket.Bind(new IPEndPoint(IPAddress.Any, 4530));
//启动监听，并且设置一个最大的队列长度
socket.Listen(4);
//开始接受客户端连接请求
socket.BeginAccept(new AsyncCallback(ClientAccepted), socket);
Console.WriteLine("Server is ready!");
Console.Read();
}

public static void ClientAccepted(IAsyncResult ar)
{
var socket = ar.AsyncState as Socket;

//这就是客户端的Socket实例，我们后续可以将其保存起来
var client = socket.EndAccept(ar);
//给客户端发送一个欢迎消息
client.Send(Encoding.Unicode.GetBytes("Hi there, I accept you request at " + DateTime.Now.ToString()));
//实现每隔两秒钟给服务器发一个消息
//这里我们使用了一个定时器
var timer = new System.Timers.Timer();
timer.Interval = 2000D;
timer.Enabled = true;
timer.Elapsed += (o, a) =>
{
//检测客户端Socket的状态
if(client.Connected)
{
try
{
client.Send(Encoding.Unicode.GetBytes("Message from server at " + DateTime.Now.ToString()));
}
catch(SocketException ex)
{
Console.WriteLine(ex.Message);
}
}
else
{
timer.Stop();
timer.Enabled = false;
Console.WriteLine("Client is disconnected, the timer is stop.");
}
};
timer.Start();
//接收客户端的消息(这个和在客户端实现的方式是一样的）
client.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(ReceiveMessage), client);
//准备接受下一个客户端请求
socket.BeginAccept(new AsyncCallback(ClientAccepted), socket);
}

static byte[] buffer = new byte[1024];
public static void ReceiveMessage(IAsyncResult ar)
{
try
{
var socket = ar.AsyncState as Socket;
var length = socket.EndReceive(ar);
//读取出来消息内容
var message = Encoding.Unicode.GetString(buffer, 0, length);
//显示消息
Console.WriteLine(message);
//接收下一个消息(因为这是一个递归的调用，所以这样就可以一直接收消息了）
socket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(ReceiveMessage), socket);
}
catch(Exception ex)
{
Console.WriteLine(ex.Message);
}
}