UdpClient socket issues, pls help!

[mce]

Hi,

I am creating an application that talks to 2 other applications, A and B. So I am creating a 2 udp sockets bind to two different ports, udpClient1 socket receive from port 12345 from application A. Upon receiving this data, i do something and use udpClient2 socket (bind to 6789) to send new data to port 54321 to application B. In the main thread, I am also listening for data that comes in from B, to the port that i am sending it data.

 IPEndPoint RemoteEp2 = new IPEndPoint(myPcIp, 54321);
void Test()
{

   udpClient1 = new UdpClient(12345);
  udpClient1.BeginReceive(receiveCallback1 , udpState);

  udpClient2 = new UdpClient(6789);
  udpClient2.BeginReceive(receiveCallback2 , udpState);

}
 
void receiveCallback1 (IAsyncResult asyn)
{
//receive from application A from port 12345
udpClient1.EndReceive(asyn, ref RemoteEp1); 
.....

//send to application B at port 54321 
udpClient2.Send(data,length,RemoteEp2); //this may send to unbound socket in the remote

//restart to receive again
  udpClient1.BeginReceive(receiveCallback1 , udpState);
}

  void receiveCallback2(IAsyncResult asyn)
{

//receive from application B send to port 6789 (where udpClient2 bind to)
udpClient2.EndReceive(asyn, ref RemoteEp); //remote host closed exception here!
.....
//restart to receive again
udpClient2.BeginReceive(receiveCallback2 , udpState);
}

I found out that the exception is due to udpclient2 sending to an unbound remote ip endpoint in the Test () method. And this ended up an socket error/exception which caused the receiveCallback to be called, as the remote end point is actually my local PC.
My question is how to handle this?? I want to use asynchronous socket and i need to used the same socket for sending and receive.