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{    /// <summary>    /// SendCommand 的摘要说明。    /// </summary>    public class SendCommand    {        /// <summary>        /// 要发送的命令文本        /// </summary>        private string m_CmdText;
        /// <summary>        ///         /// </summary>        private static readonly int BUF_SIZE=0x10000;
        /// <summary>        /// 本地UDP对象        /// </summary>        private Socket m_Client ;
        /// <summary>        /// 本地端口(也可以不设)        /// </summary>        private int m_LocalPort;
        /// <summary>        /// 远程端口        /// </summary>        private int m_RemotePort ;
        /// <summary>        /// 远程IP        /// </summary>        private string m_RemoteIP ;
        /// <summary>        /// 对方网络节点        /// </summary>        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;            }        }
    }}

董川民