I am building an application that needs to run a TCP server on a thread other than the main. When trying to run the following code:

reactor.listenTCP(ServerConfiguration.tcpport, TcpCommandFactory())
reactor.run()

I get the following error

exceptions.ValueError: signal only works in main thread

Can I run the twisted servers on threads other than the main one?

Twisted can run in any thread - but only one thread at a time. If you want to run in the non-main thread, simply do reactor.run(installSignalHandlers=False). However, you cannot use a reactor on the non-main thread to spawn subprocesses, because their termination will never be detected. (This is a limitation of UNIX, really, not of Twisted.)