New implementation of Arpanet NCP

This is a new implementation of the Arpanet NCP protocol. I have tested it across a network of emulated IMPs and an ITS host. A telnet client and server is provided and can talk to its friends on ITS.

The idea is to revive as many host operating systems as possible. Unfortunately, the list of know preserved NCP implementations is quite short.

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Lars, any reason think this wouldn’t work if compiled for an 8-bit micro?

No reason. There is some 32-bit math, but a C compiler should handle that fine.

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By the way, since so much of Arpanet software has been lost, I think it would be good and proper to invite any newcomers to the network. Get an old NCP and make it work for your computer, compile one in C, or write something new. What if there were an “lwNCP” similar to “lwIP”? Arpanet of Things?

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I see @larsbrinkhoff has started a wiki on Arpanet and how to run it yourself in emulation, using ITS on PDP-10 and IMP on H316 - possibly both those running on SIMH.

The PDP-10 emulator must be configured to use either Arpanet or TCP/IP, and you must specify how to talk to an IMP emulator
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The IMP emulator runs on the H316 emulator in SIMH. It too must be configured properly. The IMP hardware must be enabled, the IMP software must be loaded, and you must specify how to talk to the PDP-10 emulator

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Yes. The PDP-10 emulator must be model KA10 or KL10. ITS on the KS10 dropped support for the older NCP protocol and can only do TCP/IP (and Chaosnet). So Richard Cornwell’s PDP-10 emulator in SIMH is the only option.

Likewise, the Honeywell 316 emulator with support for IMP hardware is only in SIMH.

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Scenarios for Using Arpanet Computers (in 2025)