mosh-server-upnp

#!/bin/bash
#
# Start mosh-server, but first create a port redirection in the NAT
# router (with UPnP) and delete that redirection again just before
# mosh-server exits.
#
# Created: 20 Sep 2012
# Author: Bert Bos <bert@w3.org>
# original: https://www.mail-archive.com/mosh-devel@mit.edu/msg00103/mosh-server-upnp
# tweaked to reference /usr/bin/mosh-server directly
# so that you can dump this in your ~/bin named mosh-server
# and not need to pass a --server argument to your mosh invocations

# die -- print error on stderr and exit
function die
{
  echo "$@" >&2
  exit 1
}


declare -i port=0 n

# Check if we have been given a port via the -p option.
#
for (( n = 1; n <= $#; n++ )); do
  if [ ${!n} = "-p" ]; then n=n+1; port=${!n}; fi
done

# If we don't have a valid port yet, find one that is not in
# use. Check that there is no server on this machine listening on the
# port and that it is not already redirected on the NAT box.
#
if [ $port -ne 0 ]; then
  fixed_port=true
else
  for (( port = 61000; port > 0; port-- )); do
    if ! netstat -l -n -u | fgrep -q 0.0.0.0:$port; then
      if ! upnpc -l | fgrep -q " UDP $port-"; then
	break;			# Found one!
      fi
    fi
  done
fi

# If we still don't have a port, we're in trouble
#
[[ $port -ne 0 ]] || die "Error: Could not find a free port!?"

# Redirect the port in the NAT router
#
upnpc -r $port udp >/dev/null ||\
 echo "Failed to redirect port $port. Continuing anyway..." >&2

# Make a program that executes a shell, removes the port direction
# when the shell exits, and finally removes itself.
#
UPNP_SHELL=`mktemp` || die "Error: Cannot create temporary file."
cat >$UPNP_SHELL <<-EOF
	#!$SHELL
	trap "rm $UPNP_SHELL" 0
	$SHELL
	upnpc -d $port udp >/dev/null
	EOF
chmod +x $UPNP_SHELL

# Start mosh-server
#
if [ "$fixed_port" ]; then
  /usr/bin/mosh-server "$@" -- $UPNP_SHELL
else
  /usr/bin/mosh-server "$@" -p $port -- $UPNP_SHELL
fi