C# 异步 UDP 监听器 SocketException

Question

我有一个非常简单的异步 UDP 侦听器，设置为服务，它已经运行了一段时间，但它最近在 SocketException An existing connection was forcibly closed by the remote host 上崩溃了。我有三个问题：

1. 是什么原因造成的？ （我不认为 UDP 套接字有连接）
2. 如何复制它以进行测试？
3. 我怎样才能干净地处理异常，让一切都继续工作？

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.
    }
}

recvSock.EndReceiveFrom() 行抛出异常。

Answer 1

从this forum thread看来，UDP套接字似乎也在接收ICMP消息并在收到时抛出异常。也许这对于低级状态更新很有用，但我觉得它很烦人。

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递，我已经看到了 UDP 错误。至少，我认为就是这样。我一直无法可靠地复制它。

我建议你抓住SocketException，记录它（如果你愿意的话），然后处理掉那个套接字。然后再次调用Starter：

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