Let’s start listening udp on port 2193 and host 172.16.4.105:
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sudo tcpdump -i ens18 udp port 2193 -vv -X
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Send messages to listener:
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echo -n "HELLO FROM LINUX|c" | nc -w 1 -u -4 172.16.4.105 2193
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The same step, but for windows (powershell):
Install nmap (includes netcat) before.
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echo -n "HELLO FROM WINDOWS|c" | ncat -w 1 -u -4 172.16.4.105 2193
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And we can see udp-datagrams on the listener:
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sudo tcpdump -i ens18 udp port 2193 -vv -X
tcpdump: listening on ens18, link-type EN10MB (Ethernet), capture size 262144 bytes
12:29:04.426230 IP (tos 0x0, ttl 63, id 53708, offset 0, flags [DF], proto UDP (17), length 46)
10.10.100.51.58542 > nginx.dmz.lan.2193: [udp sum ok] UDP, length 18
0x0000: 4500 002e d1cc 4000 3f11 4b3c 0a0a 6433 E.....@.?.K<..d3
0x0010: ac10 0469 e4ae 0891 001a 3f1c 4845 4c4c ...i......?.HELL
0x0020: 4f20 4652 4f4d 204c 494e 5558 7c63 O.FROM.LINUX|c
12:29:18.639641 IP (tos 0x0, ttl 128, id 2181, offset 0, flags [none], proto UDP (17), length 54)
serv1c7.dmz.lan.58297 > nginx.dmz.lan.2193: [udp sum ok] UDP, length 26
0x0000: 4500 0036 0885 0000 8011 d141 ac10 0467 E..6.......A...g
0x0010: ac10 0469 e3b9 0891 0022 6fef 2d6e 0d0a ...i....."o.-n..
0x0020: 4845 4c4c 4f20 4652 4f4d 2057 494e 444f HELLO.FROM.WINDO
0x0030: 5753 7c63 0d0a WS|c..
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The best link about the cause.