REAL Software Forums

I am currently using an UDP for communication between the realbasic application I am working on and a server, nearly everything works as intented but the error callbacks sometimes return an error with code 40 resulting in the socket being no longer operationnal.

My application runs on Mac OS X so if I trust the documentation the error code should be superior to 100 for rb errors or negative for system errors, so... what the hell 40 is ???
As a side note I also got an error 2 whil trying to send datagram without destination address/port.

The error 40 seems to be triggered when trying to send big packet, is there a limit to the UDP packets size ?
My current understading of UDP is that you can put anything in them and the network layer will decompose it before sending and recompose it at the other end, I already have in place an acknowledge system to ensure packets are received by the other end.

Any help is welcome I am really starting going crazy trying to find out what is happenning with those unknown error codes.

UDP is fast, but not reliable
Packets can be dropped without error and can arrive in any order

TCP is pretty darned fast, reliable and packets arrive in order

If you need reliability use a TCP socket

I already know that, our error control mechanism is already in place and working and using udp packets allow us to have even faster communication but my only problem is why I get undocumented error codes and what an error code 40 means on mac os x.

Trusting the documentation I should not even receive this error code but I do...

error correction ?
you do realize that TCP adds all that "for free" and even assures that packets are in order

that aside it could be an OS level error code

If the error code is not documented in RB's docs, then it is surely an OS error of some kind.

Assuming it is a Mac OS error code, error 40 would translate to dsGreeting, a code used by the classic Mac OS to display the "Welcome to Macintosh" splash screen as the computer started up. Obviously this does not make any sense in this context, so I checked error -40, which is posErr, and has something to do with I/O.

Armed with that bit of information, and your previous description of the problem, I would wager breaking it your data into manageable chunks would solve the problem, as it seems you are clogging some internal buffer somewhere.

I've run into problems with big UDP packets before and found conflicting information on the max UDP packet size. If you go over this limit the packet simply won't be sent. UDP is great for establishing client IPs and such. But, as others have suggested, I would use TCP for the actual data transmission. It will chunk the data for you and keep it in order.

you better look into the unix error codes:



Gruß
Christian

Thanks for your answers