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I have seen a lot of of WebRTC client libraries using public STUN server like below:

"stun.l.google.com:19302",
"stun1.l.google.com:19302",
"stun2.l.google.com:19302",                                                                                                                              
"stun3.l.google.com:19302",
"stun4.l.google.com:19302",

I am wondering if the servers above are dead? Because I have tried:

telnet stun.l.google.com 19302
telnet stun.l.google.com 3478

I get the following response:

telnet: connect to address 74.125.204.127: Operation timed out
telnet: Unable to connect to remote host

Same thing happens to other google STUN server in list.

I couldn't get any response, does this mean the STUN servers from Google is not usable anymore?

My question is: Is telnet like the above the correct way to determine if a service is alive or not?

closed as off-topic by EEAA, Ward, masegaloeh, HBruijn, MadHatter Jul 27 '15 at 8:42

  • This question does not appear to be about server, networking, or related infrastructure administration within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 4
    I'm voting to close this question as off-topic because is should be addressed to Google. – EEAA Jul 22 '15 at 11:57
  • 8
    Actually, it is a good question, even though it's specific to Google. And a good answer will provide a way to test a STUN server in general. Moreover that STUN server is used in any WebRTC samples, demos, tutorials etc. I think people are too hasty in downvoting questions without REALLY understanding them and knowing what it's about. – Adrian Ber Nov 2 '15 at 19:52
  • @AdrianBer this is a good question, I also wanted to know the same – Bilbo Baggins Jan 25 '17 at 9:55
  • Answer: stackoverflow.com/a/34033938 – A T Oct 16 '17 at 12:27
13

I receive a reply when sending a STUN packet to port 19302 on stun.l.google.com.

Your telnet command gets no reply because it is not speaking STUN. It will attempt to open a TCP connection, which fails because STUN is running over UDP not TCP.

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