C# UDP Sockets

[Disc330]

I have been trying for so long now to understand UDP sockets in C#, but I just can't seem to grasp it.

I have recently created an application that requires the use of a UDP server and client, and so I found some examples online and they worked fine. I implemented them into my application via copy and paste... I was amazed when it gave me different results.

I have googled around a bit to find that most peoples problems occur with their router or firewalls, which I thought could not be the case because the examples worked fine on this computer before moving them to the other application... 

I am quite clueless now whats going on. I decided to fire up a packet sniffer to see where packets where going, because they are sent... just not received...
The results came back that from source address "0.0.0.0:0" a packet was sent to destination address ":0" (yes, no IP at all... ).

I have of course coded in the IP and port I WISH to use, and previously when I was using a TCP system that worked fine using the port and IP addresses.

This is the code I use to connect to the server on the client side:

Code: [Select]

this.InnerSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);


// I have literally no idea what this is meant to do. I have tried a few IP addressed and port 0, all failed to work.
this.TmpRemots = (EndPoint)new IPEndPoint(IPAddress.Any, Port);


this.Server = new IPEndPoint(IPAddress.Parse(IP), Port);

byte[] data = new byte[6] { 0, 0, 0, 0, 0, 0 };

// For some reason, this line fixed the examples.
// Just by sending data before trying to recieve stopped the exception about needing to bind before recieving.
this.InnerSocket.SendTo(data, data.Length, SocketFlags.None, this.Server);

this.RecvThread = new System.Threading.Thread(this.RecvLoop);
this.RecvThread.Start();

And the code for the server to start up:

Code: [Select]


                this.Listener = new IPEndPoint(IPAddress.Any, this._port);
                this.sender = (EndPoint)new IPEndPoint(IPAddress.Any, 0);

                this.InnerSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);

                this.InnerSocket.Bind(this.Listener);

                this.RecvThread = new System.Threading.Thread(this.RecvLoop);
                this.RecvThread.Start();

The receive loops are very similar:

Client Receive loop

Code: [Select]

try
                {
                    BytesRecieved = this.InnerSocket.ReceiveFrom(RawBuffer, ref TmpRemots);
                }
                catch (SocketException Exc)
                {
                    switch (Exc.ErrorCode)
                    {
                        case 10054:
                            {
                                this.Disconnect();
                                break;
                            }
                    }
                }
                if (BytesRecieved > 0)
                {Process();}

And server:

Code: [Select]

int BytesRecieved = this.InnerSocket.ReceiveFrom(this.RawBuffer, ref this.sender);
                if (BytesRecieved > 0)
                {Process();}

As I was saying, the client ends up with some funky destination and the server never receives a packet to reply to.

If you have any ideas on what might be causing this, please do let me know. I don't want to have to start these classes from scratch again. UDP is making me sick.

[Disc330]

Oh, and I forgot to mention:
The port I am trying to use is port 9001, but this is what comes up in the packet sniffer:




The port its come from (3220) is wrong. the port its going to is wrong and the IP addresses are defiantly wrong. The data in the packets is accurate though. 
Too confusing for me. I don't even understand the concept of Bind though. 

[Ambercroft]

It seems from the sniffed data that you are not actually setting the IP and port #s you want to use.

[RLondon]

It's been over a year since I opened a C# IDE, and I never used UDP - but I'll take a stab at it (and probably end up learning something new, instead of helping, but oh well ).

Where is the actual code that sets the IP and port to send it to?

Also, in this code:

Code: C# [Select]

1.  
2.                 this.Listener = new IPEndPoint(IPAddress.Any, this._port);
3.                 this.sender = (EndPoint)new IPEndPoint(IPAddress.Any, 0);
4.  
5.                 this.InnerSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
6.  
7.                 this.InnerSocket.Bind(this.Listener);
8.  
9.                 this.RecvThread = new System.Threading.Thread(this.RecvLoop);
10.                 this.RecvThread.Start();
11.  

Do you possibly need to set the IP in [inline=csharp] IPEndPoint(IPAddress.Any, this._port);[/inline]??

Like Ambercroft said, because the data in the packets is right, it seems like the IP and Port just aren't being set somewhere...

[Disc330]

Ahh, I'll regret to inform that I actually lost the original code for it. I got too frustrated and decided to use a UDP client instead which was a lot smoother than a socket. I think You may both be right though... I can't recall assigning the IP or port anywhere.

I was probably attempting to make the socket listen and send on mixed up end points.