Connect several RS-232 ports into one
Such a scheme exists but it is not RS232, it would be an RS485 system.  Each device connects to a common wire pair and communication is controlled by each device having a unique address.  The main PC system would send a request to an address and only one device would respond at a time. There are RS232 to RS485 converters available. 

There are also RS232 multiplexers available that use address schemes, though these are often very bulky. 

These days there would be more modern options, such as using addressed (wireless) WiFi modules for communication.