Only thing I can think of:

http://www.tek-tips.com/viewthread.cfm?qid=428260&page=1

I was going to say that link was about IPX but my problem is with TCP/IP, but on trying IPX I've found that quake 1 won't even start on the 98 box unless I use -noipx, even though IPX is quite clearly installed. Whether that's related or a different problem I don't yet know.

There was a time my machines talked to each other and various multi-player games were set up and working... umpteen upgrades and various re-arrangements later an overhaul is clearly needed.

To cap it all I am finding the internet has a much shorter memory than I was expecting - so much stuff I used a few years seems to have disappeared. 😳

When you were hosting the game on the XP machine did you try disabling the XP firewall?

Yeah a firewall problem was what I suspected at first. I'm using Zonealarm so I set it game mode which should let everything through. Also tried it with the trusted area on the "no security" level.

Edit: Was the firewall after all - although I'd disabled Zonealarm the Windows firewall was running. Thought I had disabled it when I installed Zonealarm.

The IPX problem looks like it was because file sharing was enabled on both netbios-over-ipx and ipx itself. Or at least, setting it only for netbios seemed to be what fixed it.

Thanks for the input anyhow.