Winsock issue - Client state stuck at 6=sckConnecting

[vanarang]

Hi,

I have a single machine with 2 network adapters. I started a VB application. On my main form, I have 2 WINSOCK controls - sock1 and sock2. I have bound each control to different network adapters.

I am trying to emulate a client-server architecture on this machine. I am new to this and followed an online tutorial. Below is the code. The problem I am having is that the connection state for my sever socket (sock1) is 7, but the connection state for my client socket (sock2) is always 6=sckConnecting.

Please HELP !!!!

Thanks.

------------------------------------------------------------------------

Private Sub Form_Load()

' Close sockets is not closed
If sock1.State <> sckClosed Then
sock1.Close
End If
If sock2.State <> sckClosed Then
sock2.Close
End If

' Set protocol used for communication
sock1.Protocol = sckTCPProtocol
sock2.Protocol = sckTCPProtocol

' Set Local and Remote host properties for sock1 = server
sock1.Bind 5014, "11.12.13.14"

' Set Local and Remote host properties for sock2 = client
sock2.RemotePort = 5014
sock2.RemoteHost = "11.12.13.14"
sock2.Bind 5015, "11.12.13.15"

End Sub

--------------------------------------------------------------------

Private Sub cmdCancel_Click()

If sock1.State <> sckClosed Then
sock1.Close
End If
If sock2.State <> sckClosed Then
sock2.Close
End If

End

End Sub

--------------------------------------------------------------------

Private Sub cmdStartClient_Click()

If sock2.State <> sckClosed Then
sock2.Close
End If

' Set the client in connect mode
sock2.Connect

End Sub

--------------------------------------------------------------------

Private Sub cmdStartServer_Click()

' Close sockets if not closed
If sock1.State <> sckClosed Then
sock1.Close
End If

' Set the server in listen mode
sock1.Listen

End Sub

--------------------------------------------------------------------

Private Sub sock1_ConnectionRequest(ByVal requestID As Long)

MsgBox "Request received by client to connect. Checking current connections..."

' Check the state of the current socket connection. If not closed, close it
If sock1.State <> sckClosed Then
sock1.Close
End If

sock1.Accept requestID
MsgBox "Connection accepted"

MsgBox sock1.State
MsgBox sock2.State - This is where it shows a state of 6
End Sub

--------------------------------------------------------------------

Private Sub cmdTransmit_Click()

' Client sending the data
sock2.SendData txtDataPattern.Text

End Sub

--------------------------------------------------------------------

Private Sub sock1_DataArrival(ByVal bytesTotal As Long)

Dim temp

' Server receiving the data
sock1.GetData temp, vbString

End Sub

--------------------------------------------------------------------

Private Sub sock2_DataArrival(ByVal bytesTotal As Long)

Dim temp

' Server receiving the data
sock2.GetData temp, vbString

End Sub

--------------------------------------------------------------------

[Al42]

Are the adapters connected to each other? If not, they can't see each other, so the client can't connect to the server. (It's like trying to connect to AOL when your internet connection isn't connected to your computer.)

[vanarang]

Yes, the adapters are connected to each other. Also, Msgbox sock1.state is 7 (sckConnected).

Thanks.

[DigiRev]

Instead of using Socket.Bind for the server, try using the .LocalPort and .Listen.

ie:

sock1.LocalPort = 5014
sock1.Listen

[vanarang]

If I do not use the Bind statement, then the sock1 will have the localIP of the first adapter it sees.

The reason for using the Bind statement is that each of sock1 and sock2 are tied to different adapters.

[opus]

do you try to connect a"server" and a "client" where both are in the same .exe? Is that possible?

[vanarang]

Yes, they both are in the same exe. I will repeat your question. Is that possible?

Thanks

[opus]

On the last question I can't help, but while we are at it:
As far as I understand you have two networkcards/adapter on your pc, and you want the communicate from one card to the other, is that correct?
I wouldn't evenknow how the tell a Winsock to use one or the other card!
BuT what I'm doing is connecting my (multiple) applications on one PC via the loopbackIP (127.0.01), and I have it running!

[vanarang]

The way to have Winsock use one card or the other is by using the BIND method.

[opus]

But Bind is used for the UDP protocoll! not for TCP!

[vanarang]

Look here. It says use BIND for TCP applications

http://msdn.microsoft.com/library/de...bindmethod.asp

[opus]

According to the help of VB6 I have to take that back, seems like you'Re correct!

[opus]

Although I still believe the version out of one .EXE won't work, I'd look for the Sock"_Connect event, does it fire?, try putting some code in there.
I just had an issue where I had to use a Doevent loop, you could try that also
(use a global boolean "connect", set it to False before the client tries to connect, set the Connect=true in the sock2_connect event-sub.A nd at the end of the Sub where the client tries to connect put something like:

Do
  DoEvents
Loop until connect=True

But I still believe you need to run seperate .exe (in my case I have the code for both i n one exe, but the code runs twice with a different ID set).

[vanarang]

I made some progress this morning.

Using my original code, I separated the client and the server code first into 2 separate forms in the same project AND then into 2 separate programs. Both the times, I was able to establish a connection (sock.state = sckConnected = 7).

Before I start passing data, I wanted to see the different sock properties.

The server properties (localIP, localPort, remoteIP and remotePort) were correct before and after the connection.
Local IP = 11.12.13.14 Remote IP = 11.12.13.15
Local Port = 5014 Remote Port = 5015

The client properties were correct before the connection. However, after the connection was made, the client properties were
Local IP = 11.12.13.14 Remote IP = 11.12.13.14
Local Port = 5015 Remote Port = 5014
Remote IP

Can anyone explain to me why the LocalIP for the client was correct before the connection, but changed after the connection?

Thanks. (Special thanks to opus for suggesting me to have separate exe)

[opus]

Funny thing with the IP, did you really connect the two networkcards via a cable (directly by crossed cable or via a switch or hub)?

BTW if your question is answered please mark the tread as solved (edit original post and change the topic or put checkmark to on), also ratings are welcome!

[dilettante]

I don't think you ever did have a problem. You were simply checking the State of sock2 before it had a chance to change!

Adding this would have made things clearer:

Private Sub sock2_Connect()
    MsgBox sock2.State 'It'll show 7 here!
End Sub

You were caught up in sock1_ConnectionRequest, and until exiting and returning control to the message loop sock2 couldn't respond to the accepted connection and update its State value.

You don't need 2 EXEs at all.


In cmdStartClient_Click you Close sock2, basically terminating the Bind. Then you re-open via Connect. This picked up the "first" adapter bound to the TCP/IP protocol.

[vanarang]

Responding to your second recommendation.

The sequence for the client that I have in the code above is BIND - CLOSE - CONNECT. As per your recommendation, I changed to CLOSE - BIND - CONNECT.

Using this, I am getting an error "Invalid operation at current state" when I am trying to CONNECT.

Any other things I can be trying out?

Thanks for your inputs.

[vanarang]

Another interesting thing...if I change the order of my network adapter bidnings, I get the right IPs, but now, the cleint cannot connect to the server at all.

[dilettante]

Sorry, I guess I wasn't clear about this.

My point was that the Winsock control's Bind and Connect methods are not precisely the same as the underlying Winsock library's Bind function. What this means is that you cannot use the Bind method for a client socket through the Winsock control.

To accomplish what you want to do you may have to use calls into the Winsock library. This may give you the ability to connect to a remote port using a specific local adapter specified by IP address.

By doing the Bind on the client socket you're setting it up as a server connection. By Close-ing it you undo this, then when you Connect you initiate a client connection... once again using the "first" IP channel available to Windows.

If you do that Bind on the client it will "Bind" the socket and then cause the State to go to 1 (open). You can't Connect when a socket is in this State.

[dilettante]

Regarding your most recent post, I suspect it has something to do with routing. To establish a connection through an adapter that isn't in the default routing path you'll have to provide more complex routing directions to Windows.

You can get an idea of the complexity by typing route print at a command prompt.

Networking for multihomed machines can get complicated. I think you're fighting the default behaviors and I'm not sure how much payback you're going to see even if you overcome these issues.