bug when switching from wifi web client to web server

Hello everybody,

I am trying to use my arduino mega 2560 with wifi shield as web client and web server. I combined the example "wifi simple web server" and "wifi web client". The program set my arduino as web server. This works. Via the serial interface I can set the arduino as web client when I push the "a" key. It works also. After that, the program goes back in the loop and configures the arduino back as web server. From this moment Arduino is not working anymore as web server. When I try to access it from the browser I see the blue wifi led flashing but no answer from arduino (normally the blue led flashes again when arduino answer). If I set the arduino as client again (by pushing the "a" key), I see that the answer that arduino gets is the request from my browser when I tried to reach arduino when he was configured as server followed by strange icons. After that arduino gets the answer it normally should get from the server it connects onto. Despire that the web server mode is still not working. Only a reset is needed to get arduino working again as server. I have the feeling that there is something which hold arduino in client mode instead of putting it back to server. Maybe a variable the server and client mode share? I checked the wifi library and tried to use the flush function but nothing helped. I hope somebody can help me.
You can find my code below.

Regards,
Axel

#include <SPI.h>
#include <WiFi.h>

char ssid[] = ""; // your network SSID (name)
char pass[] = "
*"; // your network password
int keyIndex = 0; // your network key Index number (needed only for WEP)
char server_IP[] = "www.google.com";
unsigned long test_flag=0;
int i=0;
int status = WL_IDLE_STATUS;
WiFiClient client_IP;
WiFiServer server(80);

void setup() {
Serial.begin(9600);
pinMode(9, OUTPUT);

// check for the presence of the shield:
if (WiFi.status() == WL_NO_SHIELD) {
Serial.println("WiFi shield not present");
while(true); // don't continue
}

// attempt to connect to Wifi network:
while ( status != WL_CONNECTED) {
Serial.print("Attempting to connect to Network named: ");
Serial.println(ssid); // print the network name (SSID);

// Connect to WPA/WPA2 network. Change this line if using open or WEP network:
status = WiFi.begin(ssid, pass);
// wait 10 seconds for connection:
delay(10000);
}
server.begin(); // start the web server on port 80
printWifiStatus(); // you're connected now, so print out the status
}

void loop() {

if(Serial.available() > 0){
byte inChar;
inChar = Serial.read();

if(inChar == 'a'){
Serial.println("\nStarting connection to dnsdynamic...");
// if you get a connection, report back via serial:
if (client_IP.connect(server_IP, 80)) {
Serial.println("connected to server");

client_IP.println("GET / HTTP/1.1");
client_IP.println("Host:www.google.com");
client_IP.println("Connection: close");
client_IP.println();

}
else {
Serial.println("connection failed");
Serial.println();
}
int b = client_IP.available();
while(client_IP.connected() && !client_IP.available()) delay(1); //waits for data
while (client_IP.connected() || client_IP.available()) { //connected or data available
char c = client_IP.read();
Serial.print(c);
//Serial.println(b,DEC);
}

Serial.println();
Serial.println("disconnecting.");
Serial.println("==================");
Serial.println();
client_IP.flush();
client_IP.stop();

}

}
client_IP.flush();
WiFiClient client = server.available(); // listen for incoming clients
//test_flag=test_flag+1;
//Serial.println(test_flag,DEC);

if (client) { // if you get a client,
Serial.println("new client"); // print a message out the serial port
String currentLine = ""; // make a String to hold incoming data from the client
while (client.connected()) { // loop while the client's connected
if (client.available()) { // if there's bytes to read from the client,
char c = client.read(); // read a byte, then
Serial.write(c); // print it out the serial monitor
if (c == '\n') { // if the byte is a newline character

// if the current line is blank, you got two newline characters in a row.
// that's the end of the client HTTP request, so send a response:
if (currentLine.length() == 0) {
// HTTP headers always start with a response code (e.g. HTTP/1.1 200 OK)
// and a content-type so the client knows what's coming, then a blank line:
client.println("HTTP/1.1 200 OK");
client.println("Content-type:text/html");
client.println();

// the content of the HTTP response follows the header:
client.print("Click <a href="/H">here turn the LED on pin 9 on
");
client.print("Click <a href="/L">here turn the LED on pin 9 off
");

// The HTTP response ends with another blank line:
client.println();
// break out of the while loop:
break;
}
else { // if you got a newline, then clear currentLine:
currentLine = "";
}
}
else if (c != '\r') { // if you got anything else but a carriage return character,
currentLine += c; // add it to the end of the currentLine
}

// Check to see if the client request was "GET /H" or "GET /L":
if (currentLine.endsWith("GET /H")) {
digitalWrite(9, HIGH); // GET /H turns the LED on
}
if (currentLine.endsWith("GET /L")) {
digitalWrite(9, LOW); // GET /L turns the LED off
}
}
}
// close the connection:
client.stop();
Serial.println("client disonnected");

}
}

void printWifiStatus() {
// print the SSID of the network you're attached to:
Serial.print("SSID: ");
Serial.println(WiFi.SSID());

// print your WiFi shield's IP address:
IPAddress ip = WiFi.localIP();
Serial.print("IP Address: ");
Serial.println(ip);

// print the received signal strength:
long rssi = WiFi.RSSI();
Serial.print("signal strength (RSSI):");
Serial.print(rssi);
Serial.println(" dBm");
// print where to go in a browser:
Serial.print("To see this page in action, open a browser to http://");
Serial.println(ip);
}

I am having a similar problem and have not figured out a solution. Even if I tell the Arduino to disconnect from WiFi and reconnect the web server still doesn't respond. I would be very interested if anyone has ideas on what might be going on!

After switching to client mode, I don't see a call to server.begin() again, to get back to server mode. Did I miss it?

My code first does a request using the webclient, then stops the client, and then starts the server. If I remove the code in the setup method that deals with the webclient then the server works without issue.

void setup()
{
	... // initialize a bunch of stuff and connect via WiFi
	
	if (client.connect(myserver, 80)) {
		Serial.println("connected to server");
		// Make a HTTP request:
		client.println("GET " + requestUrl + " HTTP/1.1");
		client.println("Host:" + hostname);
		client.println("Connection: close");
		client.println();
		delay(1000);
		while (client.available()) {
			char c = client.read();
			Serial.write(c);
		}
		client.stop();
	}
	Serial.println("\nStarting web server...");
	webserver.begin();
}

void loop()
{
	char buffer[200];
	int len = sizeof(buffer);
	webserver.processConnection(buffer, &len);
}

I would change this

		delay(1000);
		while (client.available()) {
			char c = client.read();
			Serial.write(c);
		}
		client.stop();

to this

                while(client.connected()) {
		   while (client.available()) {
			char c = client.read();
			Serial.write(c);
		   }
                }
		client.stop();

Does the server start then? There is no timeout in that code if the connection breaks (hardware fail).

edit: There seems to be a problem with the Wifi shield using multiple sockets simultaneously. I am not sure it will be able to run the server, then open a client connection at the same time as does the ethernet shield. That may cause the server to stop.

Is the server's IP address dependent on DHCP?

edit: There seems to be a problem with the Wifi shield using multiple sockets simultaneously. I am not sure it will be able to run the server, then open a client connection at the same time as does the ethernet shield. That may cause the server to stop.

I'm not trying to use a client and server simultaneously. I want to first use the client, then stop the client, then start the server and keep the server waiting for connections in the loop() method.

Is the server's IP address dependent on DHCP?

Yes. Do you think this has anything to do with the issue I'm having?

Yes. Do you think this has anything to do with the issue I'm having?

Probably not, but how will clients know what IP address has been assigned to the server?

Probably not, but how will clients know what IP address has been assigned to the server?

That is exactly why I make a request from the Arduino client before starting the server! In the request are URL parameters containing the assigned IP address. In a sense the Arudino "registers" its address with another server.