Ok this has driven me crazy for several days now. We have a specialized
telnet client application that has never given us any trouble for the last 3
years. It runs on a WIN2K workstation with a single NIC and an internal LAN
connection to access over 60 internal devices on port 23. We had to add
another device for it to access, but this device is outside the LAN and
behind a firewall so a Microsoft Networking VPN connection was introduced to
allow the connection to this external telnet server. The specialized telnet
client sends out the connection packets but no response is ever received and
a telnet session is never established. Seems like the firewall is
preventing the return traffic from reaching us, right? Except that the
WIN2K Microsoft Telnet Client that runs in a command prompt window has no
trouble at all getting an immediate connection across the VPN to the device.
To isolate somewhat, yesterday we created a test client application whose
only job is to run from a command prompt window and do a socket "connect" to
that external device on port 23. The request goes out, but no response is
received and the socket connection never gets established. Yet the
Microsoft Telnet Client from the very same command prompt window can connect
no problem.
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