rtmpdump using .bat file

[rossifeder]

hello

I did a script to stream some channels and it work, I used :

rtmpdump -v -r rtmp://xxx -a xxx -y xxx -W wwww -p ZZZZ -f xxx | vlc -

so first start rtmpdump (with all his log like connecting etc etc ) + start vlc and i wait 5 sec then the stream work

ok good

but i want to do this differently, I want to start rtmpdump and wait
if there is a connection then start vlc to watch the stream
if there is no conecction (server error , no internet, wrong url , etc etc) then write (echo) there is no stream & exit

i am searching this on internet in last 3 days and i cant find a solutin

if there is a value the rtmpdump can return o there is an external programm.exe that i can use in my .bat file
i would accept any suggestion to do this

i cant figure out how to do this
plz help me