Accepting on a specific port

I am listening on specific port for incoming connection requests. Because this port is known I am able to modify the "port forwarding" on the router to send requests to the correct computer.

However, when the ACCEPT method is called for the WinSock control it randomly picks a port. How do I specify the port I want to use for the ACCEPT method?

If I can manually select the port then I am able to open a specific block of ports on the router.

Any help would be appreciated.

Thanks.

Quote:

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Originally Posted by hiddenndangerus

However, when the ACCEPT method is called for the WinSock control it randomly picks a port. How do I specify the port I want to use for the ACCEPT method?

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The connection(s) will be accepted on the port that you are listening on.

Aside from that, I'm not 100% sure what you are trying to do.

Are you refering to the data socket on the server end?

Normally when you accept an incoming connection requestion you use the LocalPort of ZERO (0). The newly created connection uses a random port number leaving the original port for listening.

For example: Create a socket listening on port 4001. When a connection request comes in you accept it using a new socket. The newly created socket connection uses a random port number (say 1512).

What I want to do is leave port 4001 for listening and have the connections use ports 4002, 4003, 4004...etc. That way I know which ports I have to forward on the router.

You can (and should) set the LocalPort to zero in the client so that the system will assign an unused port.

When you set the LocalPort to zero in the server, the new control will still accept the connection on the port that the listener is using.

Take a look at the attached bmp. It is a screen capture of a C/S demo that I did when I was teaching myself sockets programming in VB and working out the details of sending UTDs. You will see that all four of the server's Winsock controls are using port 5556.

Here is the ConnectionRequest code:

VB Code:

Private Sub tcpServer_ConnectionRequest(Index As Integer, ByVal requestID As Long)
   Dim indx As Integer
   
   If Index = 0 Then
      ' If we already have max connections, ignore this request
      If ClientCount = MaxUsers Then
         RequestLog.Text = RequestLog.Text & "Max connects - connection refused" & vbCrLf
         Exit Sub
      End If
      ' look for an available socket
      For indx = 1 To MaxUsers
          If Not cntlLoaded(indx) Then
             ' all existing sockets are busy - create a new one
             cntlLoaded(indx) = True
             Load tcpServer(indx)
             tcpServer(indx).Close
             ClientCount = ClientCount + 1
          End If
          If tcpServer(indx).State = sckClosed Then
             ' Accept the request with the requestID parameter.
             tcpServer(indx).LocalPort = 0
             tcpServer(indx).Accept requestID
             reqIds(indx) = requestID
             cmdAccept(indx - 1).Enabled = True
             cmdReject(indx - 1).Enabled = True
             Exit For
          End If
      Next indx
      RequestLog.Text = RequestLog.Text & "Connection accepted - ID #" & requestID & vbCrLf
   End If
   
End Sub

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