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ncat cannot listen to multiple UDP clients #1223
Description
Hi,
I have a simple program that sends a message to UDP port. I'd like to use ncat to monitor it. The program itself opens a new UDP connection each time it sends a new message, so it seems that ncat is not able to handle multiple clients at the same time since I only see the message received from the very first client and only once.
ncat -ul 1234
After showing the first message, ncat hangs. If I hit enter it prints out:
Ncat: An existing connection was forcibly closed by the remote host
In case of macOS and netcat everything works fine with a very small timeout, i.e: nc -ul 1234 -w 1, same trick doesn't work with ncat though.
Activity
si74 commentedon Sep 29, 2020
I'm experiencing the same issue on Ubuntu 20.04
dmiller-nmap commentedon Oct 10, 2022
This has been expected behavior. Traditional and OpenBSD netcats also have this limitation. However, I have updated Ncat to be able to support multiple UDP clients with the
--keep-openor-koption. The commit message will close this issue when it is synced.Enable multiple UDP connections in listen mode. Fixes nmap#1223
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Address netcat 7.94 changes.
tests: Skip EDNS test if the scapy version doesn't support it.