C# 异步 UDP 侦听器 SocketException

Question

我有一个非常简单的异步 UDP 侦听器，设置为服务，并且它已经工作了一段时间，但它最近因 SocketException 现有连接被远程主机强制关闭而崩溃。我有三个问题：

1. 这是什么原因造成的？ （我不认为 UDP 套接字有连接）
2. 出于测试目的，我如何复制它？
3. 我怎样才能干净地处理异常，以便一切都能继续工作？

我的代码如下所示：

private Socket udpSock;
private byte[] buffer;
public void Starter(){
    //Setup the socket and message buffer
    udpSock = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
    udpSock.Bind(new IPEndPoint(IPAddress.Any, 12345));
    buffer = new byte[1024];

    //Start listening for a new message.
    EndPoint newClientEP = new IPEndPoint(IPAddress.Any, 0);
    udpSock.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref newClientEP, DoReceiveFrom, udpSock);
}

private void DoReceiveFrom(IAsyncResult iar){
    try{
        //Get the received message.
        Socket recvSock = (Socket)iar.AsyncState;
        EndPoint clientEP = new IPEndPoint(IPAddress.Any, 0);
        int msgLen = recvSock.EndReceiveFrom(iar, ref clientEP);
        byte[] localMsg = new byte[msgLen];
        Array.Copy(buffer, localMsg, msgLen);

        //Start listening for a new message.
        EndPoint newClientEP = new IPEndPoint(IPAddress.Any, 0);
        udpSock.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref newClientEP, DoReceiveFrom, udpSock);

        //Handle the received message
        Console.WriteLine("Recieved {0} bytes from {1}:{2}",
                          msgLen,
                          ((IPEndPoint)clientEP).Address,
                          ((IPEndPoint)clientEP).Port);
        //Do other, more interesting, things with the received message.
    } catch (ObjectDisposedException){
        //expected termination exception on a closed socket.
        // ...I'm open to suggestions on a better way of doing this.
    }
}

在recvSock.EndReceiveFrom() 行引发异常。

Answer 1

来自此论坛帖子，看来UDP套接字也在接收ICMP消息并在接收时抛出异常。也许这对于低级别状态更新很有用，但我发现它很烦人。

首先，定义幻数

public const int SIO_UDP_CONNRESET = -1744830452;

然后设置低级 io 控制以忽略这些消息：

var client = new UdpClient(endpoint);
client.Client.IOControl(
    (IOControlCode)SIO_UDP_CONNRESET, 
    new byte[] { 0, 0, 0, 0 }, 
    null
);

Answer 2

如果数据包以某种方式被截断或未完全传送，我已经看到 UDP 的错误。至少，我认为就是这样。我从来没能可靠地复制它。

我建议您捕获 SocketException，记录它（如果您愿意），然后处理该套接字。然后再次调用 Starter：

catch (SocketException)
{
    // log error
    udpSock.Close();
    Starter();
}