[erlang-questions] UDP active socket timeout

[Bogdan Andu]

this is easy on client side but on the server side there must be an
interaction
with spawned processes that actually use that socket to send data.

other thing I found hard to achieve in UDP is:
 - to detect if a client is connected from what ports;
 - sending detection errors from server to client :
   gen_udp:send/4 always returns ok no matter what if port and/or ip is
wrong.
   otherwise it would have been easy to implement something pinging the
client with an empty udp packet
   and (possibly, again) to receive response;
- gen_udp:recv is blocking (and with Timeout parameter even worse) and thus
a design based on passive sockets leads to      serialized processing of
client requests;
- if controlling process is used to handle other messages (from child
procs) other then {udp, ...} message it would be
  unpractical from parallelization point of view of client request
processing

On Thu, Feb 4, 2016 at 4:43 PM, Sean Cribbs <seancribbs@REDACTED> wrote:

> UDP is a connection-less datagram protocol, so there's no timeout inherent
> in the protocol.  However, you may have timeouts on:
>
> 1) receiving a datagram (nothing arrived)
> 2) sending a datagram (things went very badly)
>
> However, those are timeouts internal to Erlang, from your process to the
> socket driver. If you are using the {active, true} option (which it sounds
> like you are), you should use an 'after' clause in your 'receive' to
> implement timeouts, or use the trailing timeout in the return tuple of a
> gen_server/gen_fsm callback.
>
> On Thu, Feb 4, 2016 at 6:29 AM, Bogdan Andu <bog495@REDACTED> wrote:
>
>> Hi,
>>
>> How can be detected a timeout on an active UDP socket?
>>
>> controlling process receives the message:
>> {udp, Socket, Host, Port, Bin}
>>
>> and after a process is spawned to handle that data:
>> spawn(fun() -> handle_pckt(Socket, Host, Port, Bin) end),
>>
>> Q: how the spawned or controlling  process is able to detect
>> that a timeout on this UDP socket occurred ?
>>
>> documentations does not mention anything about timeout on active sockets
>>
>> Thanks,
>>
>> /Bogdan
>>
>>
>>
>>
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>>
>>
>
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