mTCP DOS Logo

TCP/IP applications for your PC compatible retro-computers

Current version: March 7th, 2020




Good news everyone! A new version of mTCP is available!

Overview

mTCP is a set of TCP/IP applications for personal computers running PC-DOS, MS-DOS, FreeDOS, and other flavors of DOS. The applications include:

mTCP runs on all variants of DOS including IBM PC-DOS, Microsoft MS-DOS, DR-DOS and FreeDOS. All of these applications will run well on the oldest, slowest PC that you can find - I routinely use them on an IBM PCjr made in 1983 because nothing beats the fun of putting a 35+ year old computer on the Internet.

People are using mTCP for goofing off and for real work. If you have a DOS machine that needs to send data across the network mTCP can help you get that done. Besides its utility to vintage computers I have heard of people using it to transfer lab data from dedicated industrial PCs, allowing backups to be run on old machines, and sending sales reports from the branch offices of a retail store to a central server.

Don't have a vintage computer laying around? No problem! mTCP applications will run in a variety of virtual and emulated environments. It has been tested with modified DOSBox builds,  VirtualBox, VMWare, and QEMU. See the documentation for the details.

Requirements

mTCP applications should work on any IBM PC compatible personal computer running DOS. To be more specific:

A packet driver is a utility that lets a program send and receive Ethernet packets using your network card. The packet driver specification is widely supported by both old and new Ethernet cards. If your Ethernet card does not have a packet driver available an NDIS or ODI driver with a "shim" to convert to the packet specification should work but that will require more memory and be slower than having a real packet driver. SLIP and PPP connections are also supported if they use a packet driver that emulates Ethernet. See http://crynwr.com/packet_driver.html for more information on the packet driver specification.

My personal testing includes:

Machines:

Ethernet adapters:
Hundreds (thousands?) of people are using mTCP on a diverse set of hardware. If your machine runs DOS and you have a packet driver for your Ethernet card, then mTCP will probably work for you.  SLIP and PPP are also supported via EtherSLIP, so any machine with a serial port can work too.

Downloads

This is the official mTCP home page. There are other sites that mirror mTCP but only this page guaranteed to have the original, unmodified binaries. Anything you find on github, ibiblio or other sites is not verified by me.

Current version: Binaries and source code available under the GPLv3 license
mTCP_2020-03-07.zip Standard binaries The mTCP applications and sample files.
mTCP_2020-03-07_upx.zip UPX compressed binaries The same as above, but the EXEs are compressed to take less disk space. Ideal for floppy based systems.
mTCP_2020-03-07.pdf User documentation The one true PDF file that will answer all of your questions.
mTCP-src_2020-03-07.zip Source code Source code and developer documentation for this release.

Release notes can be found at mTCP_2020-03-07_Release_Notes.html.

Support

mTCP is a hobby project that I started in 2005. While it is only a hobby project, I take pride in my work. If you have a comment, bug, or suggestion for a feature please email me at mbbrutman at gmail.com. I might ask for further information or a trace from the program you are having trouble with. Your bug reports help me make mTCP better for everybody else.

If you need a change to make mTCP work better for you I am interested in hearing your requirements. I am willing to write custom code if needed, but instead of charging for that service I suggest making a donation to a local animal shelter of your choice. (I have never seen an over-funded animal shelter.) Contact me with what you need and I'll see what I can do. (And thank you to those who have taken me up on this offer!)

Recent changes

Interested in seeing the source code that lets you talk directly to a packet driver? I have taken the lowest layer of the mTCP code and packaged it with a sample application that shows you how to interface a C program with the software interrupt mechanism used by packet drivers. Check it out here: mTCP_tcpacket.html

For developers

Jump in!  See the mTCP Programming Sample! http://brutman.com/mTCP/mTCP_Programming_Sample.html

All of the applications use the mTCP TCP/IP library which is designed for high performance even on small, slower machines. The code is written in a combination of C++ and assembler. The style of coding is more like "C with classes" to improve the structure of the code with assembler being used in limited areas to improve the performance. The source code is fairly well commented. You can look at it as a framework for writing TCP/IP applications for DOS, complete with plenty of examples.

Features include ARP, UDP, DNS, IP fragments, listen and accept calls for server applications, configurable buffer sizes, automatic retransmit using Karne's algorithm, and run-time switchable tracing for helping you debug. Features may be compiled in or out as needed so that you can minimize the overhead of the TCP/IP library and include only the features that you need. mTCP does not use floating point operations, avoiding the code bloat of the floating point emulation library.

mTCP is designed to be robust. DOS is a challenging environment to work in because quite frankly, it is not much of an operating system. mTCP attempts to minimize problems by using defensive programming techniques. Not every programming error can be prevented, but the library tries to help you where it can. For example, to prevent fragmentation in the DOS heap mTCP generally preallocates pools of objects and manages the objects instead of repeatedly allocating and freeing memory using the DOS heap. The FTP server and the IRC client have been demonstrated to run for days without leaking memory or crashing the machine.

High performance is a key feature of mTCP. The library is written to avoid excess memory copying wherever possible. Assembler is used on some code for both performance and to avoid making expensive library calls that will just invoke BIOS or DOS routines anyway. For the ultimate in performance you can choose to handle raw packets directly in your application layer code, or you can use higher level "send" and "recv" type calls instead. The ability to adjust buffer sizes allows you to balance speed versus memory footprint. Want to see how fast mTCP is? Here are some performance measurements for FTP and for raw socket performance: mTCP Performance notes

mTCP is only available as a library that you link with your application. A TSR version that can be used by software interrupt is not available. While a TSR version would allow more programming environments access to TCP/IP services, it is a much more difficult environment to work in and debug. Performance would also suffer too. It would be an interesting project though - if you want to collaborate on the design for a TSR version of mTCP please contact me.

(For a TCP/IP stack that loads as a TSR see Trumpet by Peter Tattam. Trumpet can usually be found by searching for TCPDRV or NTCPDRV. WATTCP is an older, more widespread TCP/IP stack that can be used as an alternative to mTCP. Neither Trumpet or WATTCP are actively maintained.)

mTCP is developed using Open Watcom, an open source tool chain that supports C, C++, and assembler. Open Watcom is flexible and generates reasonably optimized code. Open Watcom also runs under modern environments such as Windows and Linux so you can develop in the environment of your choice while still generating 16 bit DOS executables. Open Watcom is regularly updated; mTCP is using version 1.9 which was released in June 2010. Porting to other environments such as Borland Turbo C++ for DOS is possible without too much pain. (mTCP originally started with Borland Turbo C++ for DOS.)

Related resources

DOS TCP/IP Networking with Packet Drivers
A detailed tutorial on packet drivers and how they work.
Wireless Networking for Classic Machines
Use a small travel router to get your old machines using wired Ethernet onto WiFi.
Packet Driver specification
The PC/TCP Packet Driver Specification hosted by Crynwr Software.
Crynwr Software Packet Drivers
A large collection of open source packet drivers.
Georg Potthast's collection of Packet Drivers
A collection of more recent packet drivers.
OpenWatcom
The compiler used to build mTCP; runs on several platforms and cross-compiles to 16 bit DOS.


Alistair Ross: How to set up a retro DOS PC to use the web, IRC chat, email, twitter, connect to BBS's and more!
DaveJustDave: Ethernet the Easy Way on your Vintage DOS PC (YouTube)
lquessenberry: Eureka! The IBM 5150 is on the internet! (Blog)
Adam Pachulski: Connecting a 286 DOS PC to the Internet Through a Serial Connection… in 2019 (Blog)
PhilsComputerLab: MS-DOS networking with mTCP (YouTube)
Alistair Ross: The Internet connected Hot Rod IBM PC XT! (YouTube)

Older versions

These are obsolete and have been replaced with newer versions that have more features and less bugs. They are posted here for archival purposes - please don't use them.

(Obsolete) 2020-01-01 version: Binaries and source code released under the GPLv3 license
mTCP_2020-01-01.zip Standard binaries The mTCP applications and sample files.
mTCP_2020-01-01_upx.zip UPX compressed binaries The same as above, but the EXEs are compressed to take less disk space. Ideal for floppy based systems.
mTCP_2020-01-01.pdf User documentation The one true PDF file that will answer all of your questions.
mTCP-src_2020-01-01.zip Source code Source code and developer documentation for this release.



(Obsolete) 2015-07-05 version: Binaries only, source code not distributed
Standard binaries The mTCP applications and sample files.
UPX compressed binaries The same as above, but the EXEs are compressed to take less disk space. Ideal for floppy based systems.
Documentation
A single PDF file with all of the documentation.
 
(Obsolete) 2013-05-23 version: Binaries and source code released under the GPLv3 license
Standard binaries The mTCP applications, sample files and user documentation.
UPX compressed binaries The same as above, but the EXEs are compressed to take less disk space. Ideal for floppy based systems.
Source code The source code to mTCP with design documentation and notes.


Created July 29th, 2008, Last updated April 18th, 2020
(C)opyright Michael B. Brutman, mbbrutman at gmail.com