[Gambas-user] Problem with READ on a UDP socket

[Werner]

Benoit Minisini wrote:
> On mardi 4 novembre 2008, Gareth Bult wrote:
>   
>> Hi,
>>
>> I think I reported this quite a while ago but it still seems to be a
>> problem ... using READ to try to acquire less than the entire available
>> buffer doesn't seem to work .. and if I read the entire buffer, there's no
>> obvious way to break the packet down into it's constituent parts ...
>>
>> Anyone any ideas?
>> (and anyone any idea where the other 24 bytes are going ??)
>>
>> PRIVATE $udp AS UdpSocket
>>
>> PUBLIC SUB _new()
>>
>> $udp = NEW UdpSocket AS "Socket"
>> $udp.Bind(2000)
>>
>> END
>>
>> PUBLIC SUB Socket_Read()
>>
>> DIM cmd AS Byte
>> DIM siz AS Long
>>
>> PRINT Lof($udp)
>> READ #$udp, cmd, 1
>> PRINT Lof($udp)
>> 'READ #$udp, siz, 8 <= generates error if uncommented
>>
>> END
>>
>> $shell> echo "R00000011Hello World 123" |nc -u localhost 2000
>>
>> 25
>> 0 <=== "should be 24!"
>>     
>
> After having investigated, it seems that this is a property of the UDP 
> sockets.
>
> According to the manual page, when you read a message from a socket, "If a 
> message is too long to fit in the supplied buffer, excess bytes may be 
> discarded depending on the type of socket the message is received from".
>
> You should not have this behaviour if you use a TCP socket.
>
> But note that Gambas could be more user-friendly by maintaining an internal 
> message buffer for UDP sockets, so that successive READs in the same event 
> handler work as you expected. I will think about that.
>
> Regards,
>
>
>   
also, receiving udp broadcasts works only for one application. Any
additional gambas application on the same machine throws
a "Cannot bind to that socket" error.

Best Regards
Werner