The ethernet shield with webserver can suport up to four socket connetion , that mean only 4 web client request can be done at once. It is possible to hack or already exists a shield that that accept more than 4 connections at once ?
if I have several mechanisms controlled by Arduino board, which is connected to the ethernet shield, I want more friends to be able to control the various mechanisms over the internet simultaneously using only one ethernet shield (like multiplayer). can be made ?. Is possible that the ethernet shield can get more connections and can send more commands to the Arduino board at once. Arduino board can handle with more commands at the same time ?
I think this is a software limitation based on the very small amount of RAM on the Arduino board.
Each connection requires some kind of structure to hold the state of the connection and various other bits of data.
So more connections would mean more RAM usage, and less RAM for other things in the Ethernet library.
I believe it is a limitation of the Wiznet W5100 used in the EN shield.
"Supports 4 independent sockets simultaneously"
A sollution that i thought is to make arduino webserver on my pc and then the commands will be submitted to arduino via usb(because the pc can handle a much more number of request as a server) . but i don't know how to make the software that make a link (connect) between webserver and arduino board. i found same tutorials over the internet but it is verry ambiguous. If someone knows a good tutorial about this , pls reply and copy the link here.
Perhaps you could write some PHP code that accepts a request over the net, opens the serial port (with exclusive access), sends the command, then closes the port.
If more than one request arrives at a time, the open will fail because the serial port is busy. So your PHP code would just retry the open until it succeeds.
That's a crude way to serialize access to the Arduino, but it should work.
A sollution that i thought is to make arduino webserver on my pc and then the commands will be submitted to arduino via usb(because the pc can handle a much more number of request as a server) . but i don't know how to make the software that make a link (connect) between webserver and arduino board. i found same tutorials over the internet but it is verry ambiguous. If someone knows a good tutorial about this , pls reply and copy the link here.
Something simple using apache on a windows machine.
The data an arduino can serve up to one connection is so slow (4kb/sec approx), it doesn't make much sense to make it handle more than 4 connections (more than 1 to be honest). Use USB serial at 115200 baud to a real computer of some description that handles the ethernet. I use a hacked NAS box running Linux and Lighttpd (sort of a poor man's Apache) for this :
Nas box :
http://ahsoftware.de/dockstar/
Remote Arduino with ethernet shield :