TCP/IP on IBM mainframes

The purpose of this page is for information sharing about using TCP/IP on IBM mainframes.

Stacks that run on IBM Mainframes

The focus of this page will be on IBM's CS/390 which is the TCP/IP stack that the author runs at his shop.

Mainframe TCPIP interfaces:

General Links

Here are some links that are general to TCP/IP: WWW history: Here are some links that pertain to all mainframe TCP/IP stacks: We must be cautious about the Wiley Hacker:

MVS links and information:

First off, some of my pages which you might find useful:

Now for some external MVS TCP/IP information:

Web server for MVS:

Creating TCP/IP programs on MVS

Myth Shattered:

Contrary to popular belief, OS/390 can be ordered without IBM's TCP/IP stack. You can choose to
  • Order OS/390 with IBM's TCP/IP stack
  • Order OS/390 without IBM's TCP/IP stack
    • Use Sterling Software's TCP/IP stack
    • Not run a TCP/IP stack for you SNA bigots.
It's a Base Element, not an Optional Feature. It's an Optional Base Element! Think I'm making this up? Read about the OS/390 Alternate Base where you can replace some of the OS/390 Base products.

VM links and information:


As much has you would like to only support one major communication protocol on your system, you will most likely always have SNA. You might only have it for your TN3270 users but you will have SNA. If your shop has been around from the 1960's and 1970's, you might still have a few EP lines coming into a FEP (Front End Processor) to run another protocol that predates SNA.

Some SNA links for your enjoyment: Don'tcha just hate but you got stuff like this to contend with:
TCP/IP was not designed to be a robust business-oriented communication protocol. SNA WAS! APPC is a robust business-oriented communications protocol but harder to set up on both ends: Server and Client. TCP/IP is very easy to set up either the Server and the Client hence its popularity.


The code samples and advice on this page are presented asis and without warranty. Please research any advice given here and ensure that it will work in your environment.

Call for contributions, corrections, etc.

Please send me any additional TCP/IP tips that you'd like to share with others. As with all my pages, please tell me about any errors you find, bugs, etc.


My first exposure to the Internet was at my last job back in 1991 using an IBM Mainframe running good ole MVS. From TSO, we could PING, TELNET, and FTP to hosts on the Internet. This was (correct me if I'm wrong) a year or two before there were stacks for your average PC. [The idea for Windows sockets is presented at Interop Sept 1991 and the first specification for Windows Sockets Version 1.1 came in 1993.]

Here's one of my first tastes of Internet humor from an attempt to use FTP (and note the version of MVS TCP/IP):
FTPALL105I Connecting to, port 21
421- |:/:/:/|
     |      |   I'm Bart Simpson--who the hell are you?
     |      |
     | (o)(o)   Your machine isn't known to the DNS.
     C      _)
      | ,___|   Access denied to
      |   /     Please get your Zone Administrator to fix your name server
421 /      :
Our IBM rep said that our network guy was the first one to get TCP/IP working on MVS in Dallas (and without IBM help which was rare in those days). I remember hearing him over the cubicle wall "I can PING it! I can PING it!". TCP/IP for MVS communicated through the Cisco router on the white floor (which used a Mac Plus for its console).

At my next (current) job when I heard we were bringing in TCP/IP (1993), I jumped at the chance to install it. We also got TCP/IP for VM so our Officevision clients could send Internet e-mail. On MVS, I ran the freeware Gopher (the predecessor to Web Servers and the World Wide Web) server to serve out MVS text data. I remember having a discussion with another guy about this new technology called the WWW that was looking to replace Gopher. A little bit later, we installed our company's first web server, the freeware VM HTTPd written by Rick Troth, on the good old dinosaur mainframe.

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Last Updated: 2000-05-27
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