The DigiCHANNEL NC/CON-16 would be appropriate for your
application.

The DigiCHANNEL NC/CON-16 is an intelligent network concentrator
for multiuser workgroups that connects 16 serial ports over a
TCP/IP ethernet network.  It can be used alongside any other
product in the DigiCHANNEL line of connectivity solutions.

Please press "DISPLAY INFO" to view a more detailed description
of the DigiCHANNEL NC/CON-16.  Press "PRINT INFO" to receive a
hard copy.