Android ServerSocket Port Selection

Question

I'm trying to figure out how the Android OS assigns ports via the ServerSocket constructor.

(Link: http://developer.android.com/reference/java/net/ServerSocket.html)

Specifically, using the 2nd constructor, the documentation claims that "If port == 0, a port will be assigned by the OS." Does anyone know how this port is assigned by the Android OS? Based on running a significant amount of netstat -a commands on the Android terminal, it appears to be a random selection.

Can anyone confirm this? I'd like to know what I can expect when a 0 is entered for this parameter.

Thanks in advance!

I don't know the specifics, but seeing as Android is Linux underneath, this may be informative: https://idea.popcount.org/2014-04-03-bind-before-connect/#port-allocation — Barend, Aug 26 '14 at 18:01

Simas · Answer 1 · 2014-08-26T18:27:42.463

1

As per java documentation:

A port number of 0 means that the port number is automatically allocated, typically from an ephemeral port range.

Android documentation suggests that OS chooses the port for you:

If port == 0, a port will be assigned by the OS

Basically it will choose a random free port.

Some extra: This site that contains a list of ports and service who use it.

edited Aug 26 '14 at 18:27

answered Aug 26 '14 at 18:21

Simas

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It will choose a random port that is not in use already. Nothing 'open' about it. – user207421 Aug 26 '14 at 18:24
@EJP yep, my bad. Should have wrote free. – Simas Aug 26 '14 at 18:28

Android ServerSocket Port Selection

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