port 21 for non FTP

[russellbcopeland]

I have a client server process that uses ip ports via TCP to communicate and am trying to run it on port 21. I can run it fine on ports 1024 and higher though I want to run it on a lower port (many of my clients may be blocking outgoing ports above 1023 and I would like to avoind having to help them with their firewalls/proxys)

My setup is an ISA Server on Win 2K Server available to the internet, another machine (call it Mach B) that is running Win2K in my internal network. I have the port so that it is routing to Mach B successfully. I set this up for both port 21 and 1024 and 1100. I am able to connect and operate over 1024 and 1100 but not through port 21 if I am going through the internet. Another strang aspect is that my server program on Mach B logs that it is receiving a connection request, the client seems to connect but then the data that I send via TCP never gets to the server. (This is code that I wrote and am logging the conversation between client and server on a fairly low level... the conversation works correctly on 1024+ through internet and even on 21 if not going through internet.)

I have also tried connecting and transmitting over port 21 through my local network and that works fine so I am confident that it is not a setting on Mach B but something in ISA.

Any ideas? Does ISA do something special with port 21? Please help if you can!

 

[MattOP]

Did you get an answer to this?

Could be your ISP doesn't want you running Servers (ftp,smtp) from your type of connection (budget?)

 

[russellbcopeland]

I wound up just going through port 1100 and dealing with the fact that we'll be helping our clients configure routers/firewalls. Running servers from our connection is fine.. we have T1 lines and currently run a number of services such as email, several websites etc.. I was just trying to figure out a way to use a known port that would be open to accomplish the same task.. Fact is that we have to use our own protocol for the transfers.. pure ftp wont work for us (mostly business related).

Thanks though..