Two applications listening on the same port

Question

Wat happens if two applications try to listen to the same port?

The right answer is at http://stackoverflow.com/q/14388706/632951 — Pacerier, Sep 18 '15 at 09:54

score 5 · Answer 1 · answered Mar 03 '11 at 20:10

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Unless they are spawned via tcpmux, the first application binds to the port and listens for connections to it, while the second one cannot bind and cannot listen.

answered Mar 03 '11 at 20:10

adamo

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What is it that prevents the application from binding to the port? – Wintermute Mar 03 '11 at 20:36
When your application makes the relevant system call to "grab" the port, the operating system will "inform" it (via a relevant error code) that it is already taken. – adamo Mar 03 '11 at 21:17

score 3 · Accepted Answer · answered Mar 03 '11 at 20:09

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The second one that binds to the port will get an error saying something else is already listening on the port.

answered Mar 03 '11 at 20:09

carson

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Does the program check for itself if some other program is listening to the port? – Wintermute Mar 03 '11 at 20:33
The operating system does the check. – carson Mar 03 '11 at 20:41

Two applications listening on the same port

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