rtmpdump problem

[david00]

hi guys, I have a problem with rtmpdump trying to download from cam4, I tell you what I do:

1) for URL Snooper, I followed the guide of forum, but to find the rtmp I have to use the option "sniff network", otherwise I do not find.

2) open cmd as an administrator (or tried without) and insert this:
"C: \ rtmpdump \ rtmpdump.exe" -r "url snooper" -o "c: \ rtmpdump \ video.flv"
Pressing enter I get written:
Connecting .....
Info: Connected .....
the video is created, but it is always 0 bytes.

Can you help me please, What did I do wrong?