UDP Sockets, receive from

[Gregory Hassett]

I am writing a loop which will listen on a given port for incoming UDP
packets. If the UDP sender (client), terminates abnormally, then my call to
socket.BeginRec eiveFrom throws a SocketException . I catch this exception,
then re-create the socket, and re-bind it. The next time I call
BeginReceiveFro m, I get that same exception again (" An existing connection
was forcibly closed by the remote host").
When writing a simple loop to listen for UDP packets, what is the right way
to handle this exception? Here's my existing code (the async callback
"DataReceiv ed" is included, too).
Thanks

Greg
public void StartReceiveFro m ()
{
Log (string.Format ("Started UDP Receiver {0} on local port {1}", Name,
localPort));
Socket socket = new Socket (AddressFamily. InterNetwork, SocketType.Dgra m,
ProtocolType.Ud p);
try
{
IPHostEntry localHostEntry = Dns.GetHostByNa me(Dns.GetHostN ame());
IPEndPoint localIpEndPoint = new IPEndPoint(loca lHostEntry.Addr essList[0],
localPort);
socket.SetSocke tOption(SocketO ptionLevel.Sock et,
SocketOptionNam e.ReuseAddress, 1);
socket.Bind(loc alIpEndPoint);
while (true)
{
IPEndPoint remoteIpEndPoin t = new IPEndPoint (IPAddress.Any, 0);
SocketReceiveSt ateObject stateObject = new SocketReceiveSt ateObject ();
stateObject.soc ket = socket;
stateObject.rem oteIPEndpoint = remoteIpEndPoin t;
stateObject.upd Listener = this;
stateObject.nam e = Name;
EndPoint tempRemoteIpEnd Point = (EndPoint)remot eIpEndPoint;
try
{
socket.BeginRec eiveFrom (stateObject.bu f, 0, stateObject.buf .Length,
SocketFlags.Non e, ref tempRemoteIpEnd Point, new AsyncCallback(D ataReceived),
stateObject);
stateObject.don e.WaitOne();
if (stateObject.Da taReceivedExcep tion != null)
{
throw stateObject.Dat aReceivedExcept ion;
}
}
catch (SocketExceptio n ex)
{
// Log (ex.ToString()) ;
try
{
socket.Close ();
}
catch
{
}
Log ("Recreating listening socket in StartReceiveFro m()");
socket = new Socket (AddressFamily. InterNetwork, SocketType.Dgra m,
ProtocolType.Ud p);
socket.SetSocke tOption(SocketO ptionLevel.Sock et,
SocketOptionNam e.ReuseAddress, 1);
socket.Bind(loc alIpEndPoint);
}
}
}
catch (ThreadAbortExc eption)
{
Log (Name + " aborted... closing socket");
socket.Close();
}
}
public void DataReceived (IAsyncResult asyn)
{
SocketReceiveSt ateObject stateObject =
(SocketReceiveS tateObject)asyn .AsyncState;
try
{
EndPoint tempRemoteEndPo int = (EndPoint)state Object.remoteIP Endpoint;
int bytesreceived = stateObject.soc ket.EndReceiveF rom (asyn, ref
tempRemoteEndPo int);
stateObject.rem oteIPEndpoint = (IPEndPoint) tempRemoteEndPo int;
stateObject.upd Listener.OnUdpD ataReceived (new UdpDataReceived EventArgs
(stateObject.bu f, stateObject.rem oteIPEndpoint)) ;
if (AdelaP2PLib.Gl obals.LogEveryU dpSocketReceive )
{
Log (string.Format( "{0} Socket LocalEndPoint {1}, RemoteEndPoint {2}",
stateObject.nam e, stateObject.soc ket.LocalEndPoi nt, tempRemoteEndPo int));
}
}
catch (System.Net.Soc kets.SocketExce ption ex)
{
// Log (ex.ToString()) ;
stateObject.Dat aReceivedExcept ion = ex;
}
catch (ObjectDisposed Exception)
{
Log ("UdpListener.D ataReceived: Socket has been closed (probably due to
listener thread aborting)");
}
finally
{
stateObject.don e.Set();
}
}