C# 通讯中ReceiveTimeout和SendTimeout的作用

由于项目中部分代码是别人完成的,现由我接管,但紧张的编码工作基本完成后,我研究前任牛人的代码中发现有很多通讯的地方都有用到ReceiveTimeout和SendTimeout,仔细查读了一些资料才明白,ReceiveTimeout和SendTimeout的作用.

MSDN中的注释:ReceiveTimeout 属性确定 Read 方法在能够接收数据之前保持阻塞状态的时间量。这一时间的度量单位为毫秒。如果超时在 Read 成功完成之前到期，TcpClient 将引发 SocketException。默认为无超时。

在通讯过程中,由于客户端是周期性地向服务器请求数据，若客户端的请求指令或是服务端发来的数据包丢失的话，那么客户端将一直等待，陷入假死状态。由于默认为无超时,所以一定要记得设定客户端接收的超时时间，若服务器端无相应，客户端应该抛出异常，而不是毫无意义的等待。

请参考下面的代码.

using System;
using System.Text;
using System.Net;
using System.Net.Sockets;

using YD.ZYCAlarm.Buffer;

namespace YD.ZYCAlarm.UDPCommunicate
{
    ///

    /// SendCommand 的摘要说明。
    ///

    public class SendCommand
    {
        ///

        /// 要发送的命令文本
        ///

        private string m_CmdText;

        ///

        /// 
        ///

        private static readonly int BUF_SIZE=0x10000;

        ///

        /// 本地UDP对象
        ///

        private Socket m_Client ;

        ///

        /// 本地端口(也可以不设)
        ///

        private int m_LocalPort;

        ///

        /// 远程端口
        ///

        private int m_RemotePort ;

        ///

        /// 远程IP
        ///

        private string m_RemoteIP ;

        ///

        /// 对方网络节点
        ///

        private IPEndPoint m_RemoteEP ;

        public SendCommand( string strIP,int iPort,string strCmd )
        {
            this.m_RemoteIP = strIP ;
            this.m_RemotePort = iPort;
            this.m_CmdText  = strCmd;

            m_RemoteEP = new IPEndPoint(IPAddress.Parse( m_RemoteIP ) , m_RemotePort) ; 
        }

        private void  ConnectToServer()
        {
            m_Client=new Socket(AddressFamily.InterNetwork,
                SocketType.Dgram,
                ProtocolType.Udp
                );

            m_Client.SetSocketOption(SocketOptionLevel.Socket,
                SocketOptionName.ReceiveTimeout, 
                3000
                );
        }

        public bool Send()
        {
            ConnectToServer();
            
            try
            {
                Byte[] sendBytes = Encoding.ASCII.GetBytes(this.m_CmdText); 
                this.m_Client.SendTo(sendBytes ,sendBytes.Length,SocketFlags.None,m_RemoteEP) ;

                //接收服务端的回应的成功信息
                return Receive();
            }
            catch
            {
                return false ;
            }
        }

        private bool Receive()
        {
            byte[] buf=new byte[BUF_SIZE];
            EndPoint remoteEndPoint=new IPEndPoint(IPAddress.Any,0);
            
            try
            {
                int receive = this.m_Client.ReceiveFrom(buf,ref remoteEndPoint) ;
                string strData= Encoding.ASCII.GetString(buf,0,receive);

                if(strData == "OK")
                {
                    return true ;
                }
                else
                {
                    return false ;
                }
                
            }
            catch
            {
                return false ;
            }
            finally
            {
                this.m_Client.Close();
                this.m_Client = null ;
            }
        }

        public void  Dispose()  
        {
            if(this.m_Client != null)
            {
                this.m_Client.Close();
                this.m_Client = null;
            }
        }

    }
}