Comment by jolmg

The post shows use of ztcp, but zsh also has zsocket:

http://zsh.sourceforge.net/Doc/Release/Zsh-Modules.html#The-...

The difference seems to be that zsocket works with Unix domain sockets and, only for incoming connections, sockets already opened and with a file descriptor. I suppose this latter one can be used for any kind of socket if opened before exec'ing zsh.