UDP怎样检测回应是否TIMEOUT?

Question

//发送部分
 public void Send(String sMsg)
        {
            this.receive_ip();            
            System.Net.IPEndPoint iep = new System.Net.IPEndPoint(IPAddress.Parse(s_address), i_port);
            th = new Thread(new ThreadStart(receive_ip));
            th.IsBackground = true;
            th.Start();
            th.join(2500);
            byte[] a = Encoding.UTF8.GetBytes(sMsg);
            uc.Send(a, a.Length, iep);                    
        }
//接收部分
 public string Receive()
        {
            while (true)
            {               
                Data = null;                                
                if (th.IsAlive)
                {
                    uc.Close();
                    uc = new System.Net.Sockets.UdpClient();
                    Data = "timeout";
                }
                else
                {
                    Data = Encoding.UTF8.GetString(uc.Receive(ref iep));
                }                
                return Data;
            }
        } 
我这个方法检测不到TIMEOUT,各位还有什么其他方法吗?       

Answer 1

异步的还需要检测超时？下面的代码是同步的，摘自#SNMP/// <summary>
        /// Sends this <see cref="GetRequestMessage"/> and handles the response from agent.
        /// </summary>
        /// <param name="timeout">Timeout.</param>
        /// <param name="port">Port number.</param>
        /// <returns></returns>
        public IList<Variable> Send(int timeout, int port)
        {
            byte[] bytes = _bytes;
            IPEndPoint agent = new IPEndPoint(_agent, port);
            using (UdpClient udp = new UdpClient())
            {
                udp.Send(bytes, bytes.Length, agent);
                IPEndPoint from = new IPEndPoint(IPAddress.Any, 0);
                IAsyncResult result = udp.BeginReceive(null, this);
                result.AsyncWaitHandle.WaitOne(timeout, false);
                if (!result.IsCompleted)
                {
                    throw SharpTimeoutException.Create(_agent, timeout);
                }
                
                bytes = udp.EndReceive(result, ref from);
                udp.Close();
            }
            
            MemoryStream m = new MemoryStream(bytes, false);
            ISnmpMessage message = MessageFactory.ParseMessages(m)[0];
            if (message.TypeCode != SnmpType.GetResponsePdu)
            {
                throw SharpOperationException.Create("wrong response type", _agent);
            }
            
            GetResponseMessage response = (GetResponseMessage)message;
            if (response.SequenceNumber != SequenceNumber)
            {
                throw SharpOperationException.Create("wrong response sequence", _agent);
            }
            
            if (response.ErrorStatus != ErrorCode.NoError)
            {
                throw SharpErrorException.Create(
                    "error in response",
                    _agent,
                    response.ErrorStatus,
                    response.ErrorIndex,
                    response.Variables[response.ErrorIndex - 1].Id);
            }
            
            return response.Variables;
        }仅作参考。

Answer 2

我的代码是发到一个无线设备上,然后这个设备就返回一个代码,假如我SEND到设备上,但超时也拿不到回应怎么办?

Answer 3

                if (!result.IsCompleted)
                {
                    throw SharpTimeoutException.Create(_agent, timeout);
                }发送的函数会抛出超时异常。上面的代码只要正确处理这个异常就好了。收到回复，一切正常，没收到的话，在catch里面处理异常好了。

Answer 4

Lz说的超时是Server的包超时clientm没有收到还是 Client的回复包超时Server没有收到