Can RouterBoard do a serial-to-serial over IP ?

serial <-> RB450 <-> IP Tunnel <-> RB450 <-> serial

It can do one side of a TCP session. (server socket, but not server client by the looks of it, but I could be wrong, best to talk to mikrotik support I guess to get the definitive answer)

http://wiki.mikrotik.com/wiki/Serial_Po ... 7_COM_port


Alternatively have a look at, (have had good success using their serial to wifi adaptors)
http://en.usr.cn/index.php?route=produc ... ory&path=9

What is the application? I have some code that we use at work where most serial devices are connected to the production system using a serial to IP script running under linux and windows. Its pretty simple stuff.