[collectd] Collectd opens UDP port

Enrico Tröger enrico.troeger at uvena.de
Sat Oct 9 16:03:28 CEST 2010

On Fri, 8 Oct 2010 23:24:18 +1100, Amos wrote:

>2010/10/8 Enrico Tröger <enrico.troeger at uvena.de>
>> On Sun, 3 Oct 2010 06:41:14 +1000, Amos wrote:
>> >That's the way UDP works.
>> Thanks so far.
>> But could you be so kind to explain it a little further?
>> I'm not that familiar with UDP and don't see why the clients need to
>> open a listening UDP port to send data to the server.
>(Sorry, my previous reply was written on my mobile so it was short).
>For a reference, read a little about the UDP protocol -
>Basically, the packet format calls for a "source port" which must be
>filled with a legitimate value. "man 7 udp" says:
>"In order to receive packets, the socket can be bound to a local
>address first by using bind(2).
>Otherwise the socket layer will automatically assign a free local port
>out of the range defined by
>/proc/sys/net/ipv4/ip_local_port_range and bind the socket to
>I assume this happens when the first message is sent, if no port was
>assigned yet.
>So even if in this particular case there is only one-way traffic, the
>sender must have a port assigned to it.
>Hope this answers your question.

It does.
Thank you and Manuel for the information.


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