Hi All

Binding to a listening port 25 (for example) works when I run my Qt app in windows, but fails on the device, with error code 3: The address is protected

Can anyone advise how to allow opening this socket?

Your app must run as root to be able to bind to a low port number.

On all unix-style systems binding to "low ports" requires root privileges.

Edit: was too slow it seems...

Much better question: Why do you want to bind your GUI application to the SMTP (or any other) port, which usually is inhabitated by a daemon...

this app will, eventually, not be gui but will be a daemon. I'm jsut using a gui right now because I'm struggling to get the app to work as a daemon for different reasons:

when I develop windows services, because debugging them is a pain in the arse, its easier to just make a dummy gui that does nothing but embodies the service code. essentially rather than using the SCM to launch the app and call start() (and then struggle to attacha debugger to it) it is easier to open a blank window and start its message loop then have a button on the window call start().

same goes here, I'm doing a service/daemon, but I'm using the gui aspect first so that the phone shows me something i can interact with so I know its working/have a text panel to send debug messages to. eventually the app will not have a gui and will probably be configured using the browser

i think, therefore, it may be wiser to just run a high port number in the future; it doesnt really matter - the clients of this app (smtp capable programs) can always change the port number to match the app, and it may be more sensible from an exploit point of view not to have the program running as root..

thanks to all!

As people have said before, you should run in the higher port ranges as low port ranges require root priviliges. It also could be considered more secure as port scanners tend to check the lower ports for common services. Higher ports are also often unused.

You could make a separate small GUI app for the configuration (GConf can notify about key changes do your daemon can automagically react to changed configs).

Anyways, I would run the app in terminal in foreground while debugging, shorter way to a real daemon from there (and many of the daemons in linux/unix world have an option to start in foreground for exactly this reason).

Definitely the way to go as a general precaution, of course on single user device like the N900 the privilege separation does not help as much as all the important bits for the user (user data, photos, contacts etc) are accessible/messable with the users privileges...

Port 0-1024 are reserved for well defined processes, eg. http is port 80.

Use a port that's between 1025 and 65,535.

I was thinking of making the app have a web page for the few bits of configuration it would need, but I may take a look at other options including its own gui..

Using MADDE/QtC, I just click the "play" buttona nd it transfers the app to the device and runs it, hence the reason I chucked a GUI together; didnt want to build, then run a script to delopy, then run a terminal session to start the app, and do that 200 times a day

which, curiosuly enough in this case, will actually be a blessing!

Indeed, and the process I'm creating responds to SMTP commands so it is, in effect, an SMTP server.. No matter though, it can be run on a different port, because it's not as though the world is full of mail clients that cannot specify an alternate SMTP port