net/netfwd 0.4p1 OpenBSD

Netfwd is network traffic forwarder. Netfwd acts as a bridge between local and remote source. The source can be one of the following: TCP, UDP, UNIX socket and TTY device. Netfwd works with both IPv4 and IPv6 address families.

Working with TTY device means that you can redirect serial port (i.e. COM port) data to any destination. For example, it's possible to create software serial port loopback or forward serial port data to network (aka serial to network convertor).

Using this tool you can even convert one protocol into another. For example, you accept incoming connection on TCP port and forward it into UNIX socket on your local computer.