socket server not going through firewall

Posted on 2003-03-14
Medium Priority
Last Modified: 2010-04-01
I have an win32 application (not MFC) that is a socket server using winsock that handles http requests from a client.  When the server is run from within most company firewalls, the external clients are unable to connect to it.  I currently am using port 80 because I thought that would be open, but most companies turn off all ports.  How does IE and IM work through these types of firewalls.  Is there better api's to use other than winsock, or am I doing something wrong.

I have been able to use dhcp address from my isp and port forward port 80 on my linksys router to an internal ip address and that works, but most users do not have that luxury to do.

Question by:tbahr99
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Author Comment

ID: 8137230

Expert Comment

ID: 8137522
Try to reply the HTTP request from port 80 too, not from arbitrary port.

Author Comment

ID: 8137647
Looks like the broadcaster can makes http requests to an external site and back, it seems just the external clients cannot connect.
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Author Comment

ID: 8137850
Thanks Kocil for the reply, not sure what you mean.  The broadcaster never gets the accept connection for an incoming client request.

Accepted Solution

limestar earned 200 total points
ID: 8143093
You need to see the difference between connections going inwards and connections going outwards through a firewall. Port 80 is generally open for outgoing traffic through a firewall but is generally closed for inward traffic. In a sense, firewalls are there to prevent people from doing what you are trying to do - open servers on internal hosts.

So the way this is generally solved is that you only connect outwards. Thats why ICQ connects to an icq server to be able to communicate - the connection passes through the firewall since it's outbound and can then be used for bidirectional communications. So, if you want to do this kind of thing, you probably need some form of public server.

Expert Comment

ID: 9491937
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