Use netcat to serve a file through HTTP

one-shot-server.service

[Unit]
Description=One shot server using netcat
After=network.target

[Service]
Type=simple
PIDFile=/run/one_shot_server.pid
Restart=on-failure
Environment="PORT=4000"
Environment="FILE=/tmp/somefile.json"
ExecStart=/usr/bin/nohup /usr/local/bin/one_shot_server ${FILE} 0<&- &>/dev/null &

[Install]
WantedBy=multi-user.target

one_shot_server

#/bin/bash

PID_FILE=/run/one_shot_server.pid
echo $$ > ${PID_FILE}

sighandler() {
  echo "Caught signal!"
  rm ${PID_FILE}
  exit 0
}

trap sighandler HUP INT TERM

PORT=${PORT-8080}
FILE=${1}

if [[ -z "$FILE" ]]
then
  echo "The file \"${FILE}\" does not exist"
  exit 1
fi

while [[ 1 ]]
do
  { echo -ne "HTTP/1.0 200 OK\r\nContent-Length: $(wc -c <${FILE})\r\n\r\n"; cat ${FILE}; } | nc -l -p ${PORT}
done

References:

• systemd.service
• Get the pid of the shell script and save it into a lockfile;
• Best way to make a shell script daemon?
• Illustrated Redirection Tutorial
• systemd service startup issue