mbbrutman/mtcp

mTCP is a networking library and a collection of programs that let old computers running DOS, the operating system that predates Windows, connect to the internet or a local network. DOS itself has no built in idea of TCP/IP, the set of rules that lets computers talk to each other over a network, so mTCP provides that piece along with ready made applications built on top of it. This GitHub repository is a mirror of the project, which the author normally distributes as a plain ZIP file, kept here mainly so people can reference it, fork it, or follow changes over time using git. Detailed notes on how the code is organized, which compiler to use, and the overall design live in an included PDF document rather than in the README itself. Building the project requires a specific older compiler called Open Watcom, running under Windows, to cross compile the code for 16 bit DOS. Trying to build it on Linux currently runs into filename case sensitivity problems that have not yet been fixed. Each individual program lives in its own folder with its own build file, and there is an optional patch step that trims some memory usage and fixes a bug affecting a few specific vintage PC clones. If you want to use mTCP's networking code inside your own DOS project, the author suggests including it as a git submodule so you keep receiving updates, though forking the code directly works too. The author personally answers support questions by email and also runs a low volume mailing list. He is explicit that this is a hobby project done for fun, that he writes all of the code himself, and that he does not use AI for any part of it. He accepts no payment for his work, though he suggests donating to an animal shelter if you want to say thanks.