Examples of http request in unix domain socket with shell, using socat, netcat or curl

unix_socket_request.sh

#!/bin/bash

# References
# http://www.computerhope.com/unix/nc.htm#03
# https://github.com/daniloegea/netcat
# http://unix.stackexchange.com/questions/26715/how-can-i-communicate-with-a-unix-domain-socket-via-the-shell-on-debian-squeeze
# http://unix.stackexchange.com/questions/33924/write-inside-a-socket-open-by-another-process-in-linux/33982#33982
# http://www.linuxjournal.com/content/more-using-bashs-built-devtcp-file-tcpip
# http://www.dest-unreach.org/socat/
# http://stuff.mit.edu/afs/sipb/machine/penguin-lust/src/socat-1.7.1.2/EXAMPLES
# http://ubuntuforums.org/showthread.php?t=828870

# Socat (tested: Linux and macOS)
echo -e "GET /v1.18/containers/json HTTP/1.1\r\nhost: localhost\r\n\r\n" | socat unix-connect:/var/run/docker.sock STDIO

# netcat (Linux) (netcat-freebsd or netcat-openbsd for Debian)
echo -e "GET /v1.18/containers/json HTTP/1.1\r\nhost: localhost\r\n\r\n" | nc -U /var/run/docker.sock

# netcat (macOS) (gnu netcat from homebrew is not supported)
echo -e "GET /v1.18/containers/json HTTP/1.1\r\nhost: localhost\r\n\r\n" | /usr/bin/nc -U /var/run/docker.sock

# curl version
curl --silent --unix-socket /var/run/docker.sock http://v1.18/containers/json

# bonus round: relay socket (unix sock -> tcp)
socat -d -d TCP-L:8080,fork UNIX:/var/run/docker.sock

# (tcp -> unix sock)
socat -d -d UNIX-L:/var/run/httpbin.sock,fork TCP:httpbin.org:80

I get
HTTP/1.1 400 Bad Request: missing required Host header
Content-Type: text/plain; charset=utf-8
Connection: close

but printf 'GET /images/json HTTP/1.0\r\n\r\n' | nc -q 2 -U /var/run/docker.sock

returns
HTTP/1.0 200 OK
Api-Version: 1.37
Content-Type: application/json
Docker-Experimental: false
Ostype: linux
Server: Docker/18.03.1-ce (linux)
Date: Wed, 12 Dec 2018 08:43:45 GMT
Content-Length: 3

FYI: you can also use curl like: curl --silent --unix-socket /var/run/docker.sock http://v1.41/containers/json.

If you have a payload you can read it first from stdin:

body=$(cat -)
curl --silent --unix-socket /var/run/docker.sock 
 -X POST http://v1.41/containers/create
   -H 'Content-Type: application/json'
   -d "$body" 

But on the OpenWrt prior to Mar 27 2023 the curl is compiled without UNIX sockets. To check it use curl -V.
On Ubuntu it will have Features: UnixSockets but on the OpenWrt you won't see it.