Install coturn and disable it
apt -y install coturn systemctl disable coturn systemctl stop coturn
now turnutils_uclient can be used to check the connection to the turn server
turnutils_uclient -T -W <STATIC_AUTH_PASSWORD> <hostname.domain.tld>
0: Total connect time is 1 0: 2 connections are completed 0: start_mclient: msz=2, tot_send_msgs=0, tot_recv_msgs=0, tot_send_bytes ~ 0, tot_recv_bytes ~ 0 0: start_mclient: msz=2, tot_send_msgs=0, tot_recv_msgs=0, tot_send_bytes ~ 0, tot_recv_bytes ~ 0 1: start_mclient: msz=2, tot_send_msgs=0, tot_recv_msgs=0, tot_send_bytes ~ 0, tot_recv_bytes ~ 0 2: start_mclient: msz=2, tot_send_msgs=0, tot_recv_msgs=0, tot_send_bytes ~ 0, tot_recv_bytes ~ 0 3: start_mclient: msz=2, tot_send_msgs=5, tot_recv_msgs=5, tot_send_bytes ~ 500, tot_recv_bytes ~ 500 4: start_mclient: tot_send_msgs=10, tot_recv_msgs=10 4: start_mclient: tot_send_bytes ~ 1000, tot_recv_bytes ~ 1000 4: Total transmit time is 5 4: Total lost packets 0 (0.000000%), total send dropped 0 (0.000000%) 4: Average round trip delay 43.400000 ms; min = 24 ms, max = 72 ms 4: Average jitter 18.800000 ms; min = 4 ms, max = 48 ms
timeout 5 turnutils_stunclient -p 3478 hostname.domain.tld
using netcat, something like this should work for stun (see SO Link):
stunserver=hostname.domain.tld; stunport=3478; listenport=20000; echo -ne "\x00\x01\x00\x00YOGO\x59\x4f\x47\x4fSTACFLOW" | nc -u -p $listenport $stunserver $stunport -w 1; timeout 5 nc -l -u -p $listenport | head -c 32 | tail -c 4 | hexdump -e '/1 "%u" "."' | grep -o ".*[^.]" && echo yes-no-problem || echo "Error in Tun server:$stunserver:$stunport"
~~DISCUSSION~~