KB: You must call the Bind method before performing this operation.

I got this error message: "You must call the Bind method before performing this operation." when using the UDP protocol to communicate with another application. Here is the simplified code

.......
IPAddress serverIP = IPAddress.Parse("xx.xx.xx.xx");
IPEndPoint serverEP = new IPEndPoint(serverIP, 12345);
UdpClient client = new UdpClient();

//start listening
client.BeginReceive(new AsyncCallback(ReceiveCallback), serverEP);  //here causes the problem
//send message to server and wait for response
client.Send(Encoding.UTF8.GetBytes("Hello"), "Hello".Length, serverEP);
.....

After spending so many hours on this issue, I finally figure out what the problem is.
The error message already mentioned that you must Bind first! Therefore, I changed the order of the listening & sending, and it works! Here is the code that works

.......
IPAddress serverIP = IPAddress.Parse("xx.xx.xx.xx");
IPEndPoint serverEP = new IPEndPoint(serverIP, 12345);
UdpClient client = new UdpClient();

//send message to server and wait for response
client.Send(Encoding.UTF8.GetBytes("Hello"), "Hello".Length, serverEP);
//start listening
client.BeginReceive(new AsyncCallback(ReceiveCallback), serverEP);
.....

This may not be the case that you encounter. It just one of the many possibilities to solve the issue.