@echo off
:: This batch file uses the http-ping application to detect when
:: a web server is not responding, or responds with a 5XX status
:: code. It returns 0 if the server responds properly and 1 if not.
:: It is intended for use with AlwaysUp
:: (https://www.coretechnologies.com/products/AlwaysUp/)
:: or Service Protector
:: (https://www.coretechnologies.com/products/ServiceProtector/).
:: Copyright © Core Technologies Consulting, LLC. All
:: rights reserved.


:: Here are a few variables that you should adjust.
:: ** Please specify the URL you wish to ping, and the full path
:: to the http-ping executable on your system **
SET url=http://localhost:80
SET http-ping-exe-path="C:\Temp\http-ping.exe"
:: num-times-to-ping == The number of ping attempts that will be
:: made. The default of 5 is probably OK, but you can increase
:: it if errors are frequent (but tolerable).
SET num-times-to-ping=5
:: num-seconds-between-pings == The time to wait between ping
:: attempts. Increase this to give your server more time to get
:: back on its feet after an error.
SET num-seconds-between-pings=10


:: Loop "num-times-to-ping" times.
FOR /L %%X IN (1,1,%num-times-to-ping%) DO CALL :loopbody %%X


:: If we get here, then all ping attempts failed.
echo All %num-times-to-ping% attempts of http-ping failed^! ^
Exiting with 1.
exit 1


:loopbody
:: Ping your web server once, returning the HTTP status code
:: (or 0 if the ping failed to connect).
%http-ping-exe-path% -e -n 1 %url%
:: http-ping returns the HTTP status code or 0 if the ping
:: failed to connect. The list of HTTP status codes is
:: described here:
:: http://en.wikipedia.org/wiki/List_of_HTTP_status_codes
:: For this script, we'll panic on 0 or 5XX (server error)
:: and consider all other codes as a success.
IF %ERRORLEVEL% GTR 0 (
   IF %ERRORLEVEL% LSS 500 (
      echo http-ping returned %ERRORLEVEL% - not an error. ^
Exiting with 0.
      exit 0
   ) else IF %ERRORLEVEL% GTR 599 (
      echo http-ping returned %ERRORLEVEL% - not an error. ^
Exiting with 0.
      exit 0
   )
)
echo On attempt #%1, http-ping returned %ERRORLEVEL% - an error.
:: If this was not the last attempt, pause before trying again.
:: Since DOS doesn't have a "sleep" command, use ping with an
:: invalid address and a timeout (in milliseconds) to wait for
:: a while. You can adjust the timeout value
:: (num-seconds-between-pings) above.
IF %1 LSS %num-times-to-ping% (
   SET /A milliseconds=%num-seconds-between-pings% * 1000
   echo Pausing for %num-seconds-between-pings% second^(s^)^
before the next attempt...
   ping 1.1.1.1 -n 1 -w %milliseconds% > nul
)