This might indicate that another application/process already uses the same socket address (protocol, IPaddress, port) the receiver wants to bind. Or a socket that formerly bind to the IPaddress/port has not been closed properly.
First in the sender-modul I can only choose my webcam for the input. Is it possible to choose an avi-file?
you can replace the VideoIn node with a FileStream node to use an .avi file.
Second in the Receiver-modul I have to choose a stream. In which folder do I find the stream?
choose any .avi (=stream) you like that has the same dimensions than your source stream. note that you only need to do this due to vvvvs lack of handling freeframe-source-plugins correctly.
Last but not least. I see only one VideoOutWindow from the Sender-Modul. If all works right I should see two Windows, one from the sender-modul and one from the receiver-modul. Is this true?