[SOLVED] HTTP Multiple Port Forwarding with SOCAT/Bash

Issue

I am attempting to set up a shell script to listen on a port, forward to n different IP addresses, and return the result of one of those API calls.

If I have one IP address, the solution is straightforward with

socat TCP4-LISTEN:8080,fork,reuseaddr,crlf tcp4:127.0.0.1:8000

Where a REST API is on port 8000, and I am listening on port 8080.

For the multiple IP case, it seems like I need to use tee in some capacity to split into multiple API calls, as such:

socat TCP4-LISTEN:8080,fork,reuseaddr,crlf - | tee \
      >(socat - tcp4:127.0.0.1:8000 | cat; echo "This ends") \
      >(socat - tcp4:127.0.0.1:8000 | cat; echo "This ends too")
      >/dev/null

While I am able to print out the API calls from inside and the inner socat calls terminate (as This ends and This ends too are both getting printed when making a call on port 8080), the outer socat call does not return anything. Is there a way to return one of the tee values for the outer socat?

Solution

A potential solution to the problem is to create a handler script that takes the TCP-listen input and handles it.

router.sh:

socat TCP-LISTEN:8080,fork,reuseaddr EXEC:"bash -e ./route_handler.sh"

route_handler.sh:

tee >(socat - TCP4:127.0.0.1:8001 >> /dev/null) | socat - TCP4:127.0.0.1:8000

When port 8080 is hit, the results are sent to the localhost ports 8000 and 8001 are called. The output from port 8000 is returned to the TCP listener.

Answered By - Hunter B