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Huge Problem with Winsock Application

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lucyv

Programmer
Mar 11, 2002
152
US
Okay, I am having a huge problem with a winsock "chat" program I wrote in VB 6.0. I'm hoping somebody here can help me out with this problem.

A couple of years ago I wrote an application for some clients of mine. This app has a chat feature that allows users to chat with each other. I put a lot of bells-and-whistles into it (rtf color changing, sounds, a buzz feature, etc) and everyone is really happy with it.

Last week a client of mine informed me that they are using the app on about 18 workstations in their area. Everything is working fine except for one computer. For some reason this computer can start a chat session but it can not receive a chat.

Background Info: when a user wants to start a chat with a computer the system firsts pings the computer to ensure it is on the network. Once the computer is pinged, then it instantiates the chat session, which in return creates an winsock array element that handles the individual chat session.

I think it's important to note that although other computers can not start a chat with this computer, it can instantiate chat sessions with outside computer. They, in return, can reply to any instant messages, because the chat session has already been estabished, eliminating the need to ping the original (problematic) comptuer.

I first experienced some problems with Windows XP due to their internal firewall. When the firewall was turned on, no outside comptuers could ping the computer, which in return disallows for an chat sessions. Once the firewall is turned off, then everything works fine.

The strange thing is that all kind of system configurations on this computer has been turned off (I think). The reason why I say "I think" is because my client is in another state and I do not have direct access to they system.

Does anyone know what might be causing the computer from being connected/pinged to? All of the workstations have the WIN XP firewall turned off, all are on the network with the correct profile configurations, all are built using the same image, and all workstations have the Cisco VPN installed. I originally thought this was the root of the problem, but we had the VPN service disabled and it still did not solve this problem.

Can anyone help me out??? My clients are getting very impatient, and their IT technican is starting to point the finger.

Thanks in advance for your help.

-lucyv
 
Do they have a laptop with a working version of your software? If so perhaps they wouldn't mind testing by plugging it in to the ethernet port where this one PC has problems. That should rule out the physical network as the problem.

It might not solve the problem, but it will seem like a logical thing to suggest to your imatient client, and that should buy some more time to find the problem.
 
Sheco,

Thanks for your suggestion. I'm almost 100% sure it is not a physical network problem for two reasons. 1) The software requires the client to log into a SQL Server database that is on their network. The PC in question does not have a problem logging into the server. 2) None of the other PCs in the area are having the same problem. They can IM everyone else just fine.

-lucyv
 
A ping travels over UDP but I assume your "chatting" is happening over TCP?

So just because you can talk TCP doesnt mean the ping will work. Sometimes UDP is filtered on a network, especially to protect against "ping flood" denial of service attacks.

 
[blush] /blush

Maybe I should read these things before I link them! The wikipedia says that ping uses ICMP rather than UDP.

 
Should I recommend they check UDP and/or ICMP? If so, how would I word it without sounding like a newbie???

-lucyv
 
Just to let everyone know, I fixed my problem. The problem was that I could ping the computer using its IP address, but I could not ping it using its name (a DNS issue). I had my IT guy refresh the DNS database and everything works fine now.

-lucyv
 
Thanks for the update, I'm glad you got it worked out.
 
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