there is a lot of RS232 simulation software.
RS232 by itself doesn't describes software level transmission start protocol. You command manually receive send on both ends or or define one end as allways master.
The solution of RS232 "network" is made already. There are some systems, where network server listens all the ports all the time. Operator from machine tool side sends file to server. File includes the name of required part program. Server sends the file instantly.
Gateways RS232 <=> Ethernet are used there.