Reroute server path to specific port

I have a server running Ubuntu and a DNS that routes http://foo on my network to that server’s IP address, e.g. 192.168.1.123. I have several web application running on the server but there are too many ports to remember. Can I somehow route http://foo/bar to e.g. 192.168.1.123:10000?
I can’t change anything about the DNS but can edit anything on the server.