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ncat cannot listen to multiple UDP clients #1223

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pronebird opened this issue May 23, 2018 · 2 comments
Closed

ncat cannot listen to multiple UDP clients #1223

pronebird opened this issue May 23, 2018 · 2 comments

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@pronebird
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pronebird commented May 23, 2018 •
edited

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.
@si74
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si74 commented Sep 29, 2020

I'm experiencing the same issue on Ubuntu 20.04

@dmiller-nmap
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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-open or -k option. The commit message will close this issue when it is synced.

almusil added a commit to almusil/ovn that referenced this issue Mar 12, 2024
@almusil
tests: Address netcat 7.94 changes.
f6d9752 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
almusil added a commit to almusil/ovn that referenced this issue Mar 12, 2024
@almusil
tests: Address netcat 7.94 changes.
1056702 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
ovsrobot pushed a commit to ovsrobot/ovn that referenced this issue Mar 12, 2024
@almusil @ovsrobot
tests: Address netcat 7.94 changes.
a641d4c 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: 0-day Robot <robot@bytheb.org>
almusil added a commit to almusil/ovn that referenced this issue Mar 19, 2024
@almusil
tests: Address netcat 7.94 changes.
d8e47c7 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
---
v4: Rebase on top of current main.
ovsrobot pushed a commit to ovsrobot/ovn that referenced this issue Mar 19, 2024
@almusil @ovsrobot
tests: Address netcat 7.94 changes.
87f34b3 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: 0-day Robot <robot@bytheb.org>
dceara pushed a commit to dceara/ovn that referenced this issue Mar 19, 2024
@almusil @dceara
tests: Address netcat 7.94 changes.
0a35824 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
dceara pushed a commit to dceara/ovn that referenced this issue Mar 19, 2024
@almusil @dceara
tests: Address netcat 7.94 changes.
653e010 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
dceara pushed a commit to dceara/ovn that referenced this issue Mar 19, 2024
@almusil @dceara
tests: Address netcat 7.94 changes.
4f1b840 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
dceara pushed a commit to dceara/ovn that referenced this issue Mar 19, 2024
@almusil @dceara
tests: Address netcat 7.94 changes.
d26562b 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
almusil added a commit to almusil/ovn that referenced this issue Mar 20, 2024
@almusil
tests: Address netcat 7.94 changes.
816381e 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
almusil added a commit to almusil/ovn that referenced this issue Mar 20, 2024
@almusil
tests: Address netcat 7.94 changes.
a66136d 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
almusil added a commit to almusil/ovn that referenced this issue Mar 20, 2024
@almusil
tests: Address netcat 7.94 changes.
bf6e815 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
almusil added a commit to almusil/ovn that referenced this issue Mar 20, 2024
@almusil
tests: Address netcat 7.94 changes.
205f9f7 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
almusil added a commit to almusil/ovn that referenced this issue Mar 20, 2024
@almusil
tests: Address netcat 7.94 changes.
6ab98cc 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
almusil added a commit to almusil/ovn that referenced this issue Mar 20, 2024
@almusil
tests: Address netcat 7.94 changes.
4d83389 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
ovsrobot pushed a commit to ovsrobot/ovn that referenced this issue Mar 20, 2024
@almusil @ovsrobot
tests: Address netcat 7.94 changes.
6d5ac3d 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
Signed-off-by: 0-day Robot <robot@bytheb.org>
ovsrobot pushed a commit to ovsrobot/ovn that referenced this issue Mar 20, 2024
@almusil @ovsrobot
tests: Address netcat 7.94 changes.
aa52567 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
Signed-off-by: 0-day Robot <robot@bytheb.org>
dceara pushed a commit to dceara/ovn that referenced this issue Mar 20, 2024
@almusil @dceara
tests: Address netcat 7.94 changes.
a64e44e 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
dceara pushed a commit to dceara/ovn that referenced this issue Mar 20, 2024
@almusil @dceara
tests: Address netcat 7.94 changes.
a87dda6 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
putnopvut pushed a commit to ovn-org/ovn that referenced this issue Mar 20, 2024
@almusil @putnopvut
tests: Address netcat 7.94 changes.
ef214c6 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
Signed-off-by: Mark Michelson <mmichels@redhat.com>
putnopvut pushed a commit to ovn-org/ovn that referenced this issue Mar 20, 2024
@almusil @putnopvut
tests: Address netcat 7.94 changes.
e61d64a 
Fedora received an update of netcat to version 7.94, this version
brings ability for UDP to accept multiple connections without closing
(-k/--keep-open) [0]. That had negative impact on the tests as the UDP
netcat server was closing sooner that expected.

Make sure that the server is alive when we expect it to and avoid
checking kill of server that might be already finished.

[0] nmap/nmap#1223
Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 0a35824)
Signed-off-by: Mark Michelson <mmichels@redhat.com>
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3 participants
@pronebird @si74 @dmiller-nmap