WiFly shield + Arduino + auto-connect issue - wifi

Question

I'm using the WiFly shield with Arduino, and everything works fine: I upload my skecth to Arduino via USB, I connect a 9V battery, I disconnect the USB, and the wifi module transmits everything fine (it transmits data to my web server).
When the battery runs out I replace with another battery, but then the wifi/arduino no longer communicates with my server..
I'm a newbie on Arduino and I don't understand whether if every time the power is off Arduino loses the program, or simply that the wifi is not able to auto-connect...
Is this a software problem or hardware?
And if software what am I doing wrong?
This is my sketch example - I'm just sending a string to my server:
#include "WiFly.h"
#include "Credentials.h" // includes ny user:pass wifi network
Client client("[***myserverip***]", 80);
void setup() {
Serial.begin(9600);
WiFly.begin();
if (!WiFly.join(ssid, passphrase)) {
Serial.println("Association failed.");
while (1) {
// Hang on failure.
}
}
connectServer();
}
void loop() {
if (client.available()) {
char c = client.read();
Serial.print(c);
}
if (!client.connected()) {
Serial.println();
Serial.println("disconnecting.");
client.stop();
delay(60000); // check every minute
connectServer();
}
}
void connectServer() {
Serial.println("connecting...");
if (client.connect()) {
Serial.println("connected");
String query = "GET /arduino/test?q=testString HTTP/1.0";
client.println(query);
client.println();
} else {
Serial.println("connection failed");
}
}
So everything works fine but when I unplug the power and plug it back the arduino doesnt restart the process.

Answer 1

I found the solution myself - the problem was with the hardware.
The problem was in my Arduino UNO R2, there is a known bug.
I bought a UNO R3 and I don't have this problem anymore.

Answer 2

Its because Arduino board doesn't have on board power on reset when using external power supply so you will always need to reset it just after supplying power. You can put a capacitor at reset pin to eliminate this issue. But if you are using USB as a power source then USB controller will reset the Arduino so in that case you will never have this problem.