C# 异步UDP发送接收数据 C#

【C# 异步UDP发送接收数据】UDP：User Datagram Protocol 用户数据报协议，是一个无连接的传输协议。
所以不像TCP一样要使用ConnectAsync来与服务器连接，直接向服务器发送数据即可。
参考：MSDN

public bool ReceiveFromAsync (System.Net.Sockets.SocketAsyncEventArgs e); Returns Boolean true if the I/O operation is pending. The Completed event on the e parameter will be raised upon completion of the operation.false if the I/O operation completed synchronously. In this case, The Completed event on the e parameter will not be raised and the e object passed as a parameter may be examined immediately after the method call returns to retrieve the result of the operation.

简单来说就是如果返回值是true就等待处理，接收成功了会触发回调事件
如果是false就说明已经同步处理完成了，这时回调事件不会触发，需要自己手动执行。
SendToAsync也是一个道理
也就有了下面的代码：

...省略定义一些成员变量：connectSocket，endPoint 等 ...省略(构造函数，传入ip和port)... connectSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp); IPAddress address; if (!IPAddress.TryParse(ip, out address)) // 尝试解析IP，万一它是一个域名呢 { try { IPHostEntry host = Dns.GetHostEntry(ip); address = host.AddressList[0]; } catch (Exception) { Console.WriteLine("IP解析错误！"); } } endPoint = new IPEndPoint(address, port); ......省略(定义一个“发消息”方法，传入byte[] buff)... SocketAsyncEventArgs saea = new SocketAsyncEventArgs(); saea.SetBuffer(buff, 0, buff.Length); saea.UserToken = connectSocket; saea.Completed += new EventHandler(IO_Completed); saea.RemoteEndPoint = endPoint; if (!connectSocket.SendToAsync(saea)) { IO_Completed(null, saea); } ...private void IO_Completed(object sender, SocketAsyncEventArgs e) { switch (e.LastOperation) { case SocketAsyncOperation.ReceiveFrom: ProcessReceive(e); break; case SocketAsyncOperation.SendTo: ProcessSend(e); break; default: Console.WriteLine(e.LastOperation); break; } } /// /// 处理udp客户端发送的结果 /// /// private void ProcessSend(SocketAsyncEventArgs e) { if (e.SocketError == SocketError.Success) { // 发送成功就可以准备接收 byte[] buff = new buff[1024] SocketAsyncEventArgs saea = new SocketAsyncEventArgs(); saea.SetBuffer(buff, 0, buff.Length); saea.UserToken = connectSocket; saea.Completed += new EventHandler(IO_Completed); saea.RemoteEndPoint = endPoint; if (!connectSocket.ReceiveFromAsync(saea)) IO_Completed(null, saea); } else { // 发送失败 } } /// /// 处理接受到的udp服务器数据 /// /// private void ProcessReceive(SocketAsyncEventArgs e) { if (e.BytesTransferred > 0 && e.SocketError == SocketError.Success) { //处理接收到的数据(e.Buffer); } else { //没有接收到数据 } }