tmateSender.sh

#!/bin/bash

# a script that checks if connection is down for 5 minutes
# then waits till connection comes back again
# exits tmate session 
# creates a new tmate session and send session id using a telegram bot

TIME=$(date +"%c")
DOWN_TIME=0
LAST_SEEN=$(date +"%s")

MAX_DOWN_TIME=1200 # 20 minutes
SLEEP_INTERVAL=30 # 30 seconds

SITE=google.com   # SITE to check against

# Telegram Credentials
TOKEN= # bot token
CHAT_ID= # your telegram chat id
URL="https://api.telegram.org/bot$TOKEN/sendMessage"

# Interface
INTF=''

BOOT_MESSAGE="Greeting" # Greeting Message
POWERED_ON=1


func sendMessage ( ) {

	#stop previous session of tmate
	tmate -S /tmp/tmate.sock kill-sessioni 2> /dev/null
		
	#start a new tmate session
	tmate -S /tmp/tmate.sock new-session -d 2> /dev/null
	tmate -S /tmp/tmate.sock wait tmate-ready 2> /dev/null
		
	#extract the session id
	SESSION_ID=$(tmate -S /tmp/tmate.sock display -p '#{tmate_ssh}')
	LOCAL_IPV4=$(ip address show eth0 | grep "inet\b" | sed "s/^ *//" | cut -d ' ' -f 2)

	# compose the message
	MESSAGE="\[ $TIME \]
	- Session $SESSION_ID 
	- IPV4 $LOCAL_IPV4"

	#email the session id - changed to telegram
	curl -s -X POST $URL -d chat_id=$CHAT_ID -d text="$MESSAGE" 2> /dev/null
    
}

while [ true ]
do # infintely run the script

	if ! ping -c 1 "$SITE" ; then # checking if connection is down
		DOWN_TIME=$(( $(date +"%s") - $LAST_SEEN ))
	else

		if [[ $POWERED_ON -eq 1 ]]  ; then 
			curl -s -X POST $URL -d chat_id=$CHAT_ID -d text="$BOOT_MESSAGE"
			POWERED_ON=0
		fi

		DOWN_TIME=0
		LAST_SEEN=$(date +"%s")
	fi

	sleep $SLEEP_INTERVAL # lay low 

	if [ $DOWN_TIME -ge $MAX_DOWN_TIME ]; then
		
		while [ ! nc -zw1 google.com 443 ]; do 
			# loop until connection comes up
			sleep $SLEEP_INTERVAL # sleep for two minutes
		done

		sendMessage

		sleep (($SLEEP_INTERVAL * 10 )) # sleeps for 30 * 10 seconds = 6 min
		
		# reset everything
		DOWN_TIME=0
		LAST_SEEN=$(date +"%s")

	fi

done