Hello Tim,
Thank you for your reply. The program returns the port 62981 when I run the Serial.println(Udp.remotePort()); command and check the serial messages returned from the Arduino. the sender's port (computer) is also 9091. I do not understand why this is happening.
As for the IPs, the router assigns the computer the 192.168.0.101 IP and the Arduino gets 192.168.0.100.
Concerning the WiFi shield, the firmware version is 1.1.0 (I have upgrade it myself). The thing is that I need to communicate via UDP with 3 Arduino boards. is there another firmware version in the works? I use the antenna connector WiFi shield to which I have attached an antenna.
Thank you,
Jean