Connair Elro TXP script

#!/bin/bash
set -euo pipefail

PATH=$PATH:/usr/bin:/bin/
export PATH


vendor=$1
masterCode=$2
slaveCode=$3
stateCode=$4
gatewayIp=$5
gatewayPort=$6
pid=""

#######################################
# Builds a TXP string from the given arguments
# Globals:
#   None
# Arguments:
#   $masterCode $slaveCode $stateCode
# Returns:
#   $msgStr
#######################################
build_elro_txp() {
  local masterCode=$1
  local slaveCode=$2
  local stateCode=$3

  local sA=0
  local sG=0
  local sRepeat=15
  local sPause=5600
  local sTune=350
  local sBaud=25
  local sSpeed=16

  local headStr="TXP:$sA,$sG,$sRepeat,$sPause,$sTune,$sBaud,"
  local tailStr=",1,1,$sSpeed,;"
  local onStr="1,3,1,3,3"
  local offStr="3,1,1,3,1"

  local bitLow=1
  local bitHgh=3

  local seqLow="$bitHgh,$bitHgh,$bitLow,$bitLow,"
  local seqHgh="$bitHgh,$bitLow,$bitHgh,$bitLow,"

  local msg=""
  local bits=$masterCode$slaveCode
  for (( i=0; i<${#bits}; i++ ))
  do
    local bit=${bits:$i:1}

    if [ "$bit" == "0" ]; then
      local msg=$msg$seqLow
    else
      local msg=$msg$seqHgh
    fi
  done


  if [ "${stateCode,,}" == "on" ]; then
    local stateCode=$onStr
  fi
  if [ "${stateCode,,}" == "off" ]; then
    local stateCode=$offStr
  fi

  local msgStr=$headStr$bitLow","$msg$bitHgh","$stateCode$tailStr
  echo "$msgStr"
}

#######################################
# Sends a string via netcat to the gateway
# Globals:
#   None
# Arguments:
#   $msgStr
# Returns:
#   None
#######################################
send_string() {
  local msgStr=$1
  local sleepRate=0.8

  echo "$msgStr" | nc -u "$gatewayIp" "$gatewayPort" >/dev/null 2>/dev/null &

  pid=$!
  sleep $sleepRate
  kill $pid 2>/dev/null >/dev/null
  exit
}

err() {
  echo "[$(date +'%Y-%m-%dT%H:%M:%S%z')]: $*" >&2
}

# main

if [ "$1" == "" ]; then
  echo "usage: $0 vendor params ... on|off ip port"
  echo "vendors / params"
  echo "   elro masterid|m1 slaveid|s1|s2|s3"
  exit
fi

if [ "$stateCode" == "" ]; then
    err "State (on|off) is missing."
    exit 1
fi
if [ "$slaveCode" == "" ]; then
    err "Slave code is missing."
    exit 1
fi
if [ "$masterCode" == "" ]; then
    err "Master code is missing."
    exit 1
fi

if [ "$gatewayIp" == "" ]; then
    err "Gateway IP is missing."
    exit 1
fi
if [ "$gatewayPort" == "" ]; then
    gatewayPort=49880
fi

case $vendor in
  elro)
    string=$(build_elro_txp "$masterCode" "$slaveCode" "$stateCode")
    send_string "$string"
    ;;
  *)
    err "Unknown vendor."
    exit 1
    ;;
esac