CallSignal.sh

#!/bin/bash
#
#  File:     CallSignal.sh
#  Author:   Jake Dolan ([email protected])
#
#  Purpose:  Listen for incoming SIP signals on
#            a specified address and send a
#            TCP signal to another address when
#            detected. (Optional) Can be disabled
#            for specified time periods.
#
#            Should be time-disabled in unused periods
#            to reduce writing load on the filesystem.
#            This is PARTICULARLY important on Raspberry
#            Pis running on SD cards. This can be done
#            using the ENABLED_FROM and DISABLED_FROM
#            variables.


INTERFACE="eth0"
LISTEN_PHONE_ADDRESS="192.168.1.146"
CALL_SERVER_ADDRESS="192.168.1.200"
CALL_SERVER_PORT=16727

ENABLED_FROM=21600   # 21600 seconds = 6AM
DISABLED_FROM=72000  # 72000 seconds = 8PM
                     # Script will be inactive outside of these times.

function sendCallSignal () {
    signal_time=$(date +'%H:%D')
    signal=$(cksum <<< "C26SX:95AFC-$signal_time" | cut -f 1 -d ' ')
    echo "$signal" | nc -q 1 $CALL_SERVER_ADDRESS $CALL_SERVER_PORT
}

while true; do

    # Convert the current time to seconds within the day (of 86400+)
    curr_time=$(date +"%H:%M" | awk -F: '{ print ($1 * 3600) + ($2 * 60) + $3 }')

    if [ "$ENABLED_FROM" -lt "$curr_time" ]; then
        # Flush log files
        rm -rf /tmp/*.pcapng
        # Capture SIP request messages using Tshark
        tshark -n -a duration:100 -M 10000 -i $INTERFACE -Y "(sip.Method==INVITE)&&(ip.dst==$LISTEN_PHONE_ADDRESS)" -T fields -e ip.src -e ip.dst -l |
        while read -r src_ip domain_name query_type; do
            sendCallSignal
        done
    else
        sleep 5
    fi
done