Steps:
1. Open attached solution
2. Start "ChatServer.exe"
3. Start "ClientGUI.exe"
4. Press "Connect to 127.0.0.1" button in ClientGUI
==>
Client connects to server
5. Choose "UnreliableFragmented" in ChannelType in ClientGUI
6. Press "Send file: UnreliableFragmented" button
==>
Server crashes

What is going on inside:
Client sends a big message (64000 byte) via UnreliableFragmented channel but the data buffer on server side to receive message is too small (1024 byte).
It causes that all "out" variables have garbage inside. The server tries to use them and crashes.

The proper behaviour is to re-receive data again with a new buffer that is able to handle this big message. You can see that if uncomment function "ReceiveAgainIfBufferTooSmall();" in NetworkEntity.cs

Nevertheless, the "out" variables should have proper values in such case.