Commands exchange between Client and Server

[sadjoker]

I don`t understant: is there a problem to create a personal thread for every client connecting and destroy the thread when he disconnects? I have to write the same project and i`m going to do it with opening new thread for every new connection and then open separate SQL connection to the server for reading/writing data. Why you think to change that behavior with the threads?

[QAlex]

I don't think that my problem is related to server side thread. Well... maybe it is possible, but in my opinion is improbable!
I'm going to change this behaviour because of the delay between the connection and the signal connected(). If this is too long, the command id can change between the first and the second command to send... Result: only the second command is sent!
If it is difficult to understand the problem, try to imagine to call 2 times the function SomeCommand() with different cmdId:

SomeCommand(cmdId =3);
SomeCommand(cmdId = 4);

The connection starts with cmdId = 3, but signal connected() arrives late... that's why the SomeCommand(cmdId=4) is executed before the function sendCommand is executed. So only the second command is sent. Is that clear now?

[Tanuki-no Torigava]

Just a couple of things:
1. If you have to serve more than 1 client at a time or you have to run multiple commands simultaneously - use your own QThread reimplementation or have a look at QFuture.

2. Don't reopen the socket multiple times. Some firewalls consider that an attack (see SNORT for details).

3. A nice TCP/IP documentation is your friend. Just try to realize how it should work, compare to Qt implementation and you'll get that very fast.

Good luck.

[QAlex]

I implemented the solution planned some posts ago... It seems to work well!
Now all commands arrive to the server application!
However initially I've seen that 2 commands very near in time were not executed... I was really going crazy!!! Luckily, I noticed that there was also a problem in the server application: if two commands arrive at the same time, the function connected to the signal readyRead() is called only one time, and so executes only the first command.
To solve this problem, I've made a control over the socket buffer (based on the method bytesAvailable()): if at the end of the first command there are other bytes in the buffer, I call the function to read commands another time! In this way I'm sure to execute all the commands received in the buffer!
I don't know if this is the best solution... Anyway, at the moment It works!!!
If at debug time I discover some problems, surely I let you know!
Thanks for all contributions! If any of you needs some more deep explanations for this problem, ask!

See you all!
Alex