This is a simple SOCKS5 proxy server forked of and based on https://github.com/armon/go-socks5.
In particular, it allows to remap connections to particular IPs and ports.
Example:
$ socks5-server -m 1.2.3.4:5.6.7.8 -m 10.9.44.2:80:127.0.0.1:8080
This will remap requests all requests to 1.2.3.4 to 5.6.7.8 and requests
to 10.9.44.2:80 to 127.0.0.1:8080.