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# webcat - netcat for websockets
Connect to a websocket server:
webcat ws://example.com:3000/
Start a websocket server listening on port 3000:
webcat -l 3000
The server only accepts one client at a time. The client auto-reconnects.
## Setting up a MITM debugging proxy
By redirecting the standard input/output streams of webcat you can turn it into
a man-in-the-middle proxy, particularily useful for debugging stateful protocols
on top of websocket.
[some client] <-> [webcat server] <-> [webcat client] <-> [some server]
FIFOs
All it takes to set this up is four commands, for example:
mkfifo client-in server-in
webcat ws://example.com:3000/ < client-in > server-in
webcat -l 4000 < server-in > client-in
echo > server-in # unblock the FIFO deadlock
You can now connect your client to `ws://localhost:4000/`
and inject messages by writing to the named pipes:
echo "Hello from webcat" > client-in
Webcat does two tricks to make this setup even more convenient:
* When redirecting stdout, the messages are automatically printed
to stderr, so you can still observe what's happening.
* When the client recognizes the server output `accepted new client`,
it automatically disconnects and reconnects its server connection
to prevent stateful application protocols from becoming out of sync.
## Limitations
* no support for binary messages
* no support for messages containing newlines
(cannot send them, cannot distinguish them from separate messages)
* no support for WebSocket Secure (`wss://`)
(webcat is meant for local testing & debugging, wss is out of scope)
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