It can be needed to test an UDP connection with a server to ensure that connectivity is working and double check the data received.
Let’s take a simple example with a remote logstash server:
– Server mylogstash.mydomain.local
– Listening on port 5000
On emitter side, we are sending an UDP packet simulating a log line coming from an application:
echo -e '{"version": "1.1","host":"myapp.org","message":"My message","backtrace":"Backtrace of my app\n\nmore stuff"}\0' | nc -u -w 1 mylogstash.mydomain.local 5000
On receiving server side, we are executing a tcpdump to check that packet is correctly coming with good content:
# tcpdump -i any udp port 5000 -A
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes
10:43:47.621172 IP mylogstash.mydomain.local.49435 > localhost.5000: UDP, length 108
E.....@.@............./..t..{"version": "1.1","host":"myapp.org","message":"My message","backtrace":"Backtrace of my app
more stuff"}.
Here we are! It’s very simple to control UDP flows or simply check connection between 2 servers.