Last exercise "Arduino + ESP8266 - a simpe web server response with HTML" use a simple approach to find the "+IPD" in the income stream. But if fail to detect it, the buffer will not be updated, it will stop and need restart. It's another approach using readBytesUntil() to load the data to another buffer, and find "+IPD" programmatically using strncmp(). Such that if fail to detect "+IPD", it still can work for next connection.
In order to know the pattern of "+IPD" and the connection id in the incoming stream, I make a test program to show it in Serial Monitor, refer to the bottom of this post.
Due8266Web.ino
/*
Arduino Due - ESP 8266 WiFi Module
Serial (Tx/Rx) communicate to PC via USB
Serial3 (Tx3/Rx3) connect to ESP8266
Tx3 - ESP8266 Rx
Rx3 - ESP8266 Tx
ESP8266 CH_PD Connect to ESP8266 VCC
*/
#define ASCII_0 48
#define ESP8266 Serial3
String SSID = "TestAP";
String PASSWORD = "12345678";
int LED = 13;
boolean FAIL_8266 = false;
String strHTML = "<!doctype html>\
<html>\
<head>\
<title>arduino-er</title>\
</head>\
<body>\
<H1>arduino-er.blogspot.com</H1>\
</body>\
</html>";
#define BUFFER_SIZE 128
char buffer[BUFFER_SIZE];
void setup() {
pinMode(LED, OUTPUT);
digitalWrite(LED, LOW);
delay(300);
digitalWrite(LED, HIGH);
delay(200);
digitalWrite(LED, LOW);
delay(300);
digitalWrite(LED, HIGH);
delay(200);
digitalWrite(LED, LOW);
delay(300);
digitalWrite(LED, HIGH);
delay(200);
digitalWrite(LED, LOW);
do{
Serial.begin(9600);
ESP8266.begin(9600);
//Wait Serial Monitor to start
while(!Serial);
Serial.println("--- Start ---");
ESP8266.println("AT+RST");
delay(1000);
if(ESP8266.find("ready"))
{
Serial.println("Module is ready");
ESP8266.println("AT+CWMODE=1");
delay(2000);
//Quit existing AP, for demo
Serial.println("Quit AP");
ESP8266.println("AT+CWQAP");
delay(1000);
clearESP8266SerialBuffer();
if(cwJoinAP())
{
Serial.println("CWJAP Success");
FAIL_8266 = false;
delay(3000);
clearESP8266SerialBuffer();
//Get and display my IP
sendESP8266Cmdln("AT+CIFSR", 1000);
//Set multi connections
sendESP8266Cmdln("AT+CIPMUX=1", 1000);
//Setup web server on port 80
sendESP8266Cmdln("AT+CIPSERVER=1,80",1000);
Serial.println("Server setup finish");
}else{
Serial.println("CWJAP Fail");
delay(500);
FAIL_8266 = true;
}
}else{
Serial.println("Module have no response.");
delay(500);
FAIL_8266 = true;
}
}while(FAIL_8266);
digitalWrite(LED, HIGH);
}
void loop(){
int connectionId;
if(ESP8266.readBytesUntil('\n', buffer, BUFFER_SIZE)>0)
{
Serial.println("Something received");
Serial.println(buffer);
if(strncmp(buffer, "+IPD,", 5)==0){
Serial.println("+IPD, found");
sscanf(buffer+5, "%d", &connectionId);
Serial.println("connectionId: " + String(connectionId));
delay(1000);
clearESP8266SerialBuffer();
sendHTTPResponse(connectionId, strHTML);
//Close TCP/UDP
String cmdCIPCLOSE = "AT+CIPCLOSE=";
cmdCIPCLOSE += connectionId;
sendESP8266Cmdln(cmdCIPCLOSE, 1000);
}
}
}
void sendHTTPResponse(int id, String content)
{
String response;
response = "HTTP/1.1 200 OK\r\n";
response += "Content-Type: text/html; charset=UTF-8\r\n";
response += "Content-Length: ";
response += content.length();
response += "\r\n";
response +="Connection: close\r\n\r\n";
response += content;
String cmd = "AT+CIPSEND=";
cmd += id;
cmd += ",";
cmd += response.length();
Serial.println("--- AT+CIPSEND ---");
sendESP8266Cmdln(cmd, 1000);
Serial.println("--- data ---");
sendESP8266Data(response, 1000);
}
boolean waitOKfromESP8266(int timeout)
{
do{
Serial.println("wait OK...");
delay(1000);
if(ESP8266.find("OK"))
{
return true;
}
}while((timeout--)>0);
return false;
}
boolean cwJoinAP()
{
String cmd="AT+CWJAP=\"" + SSID + "\",\"" + PASSWORD + "\"";
ESP8266.println(cmd);
return waitOKfromESP8266(10);
}
//Send command to ESP8266, assume OK, no error check
//wait some time and display respond
void sendESP8266Cmdln(String cmd, int waitTime)
{
ESP8266.println(cmd);
delay(waitTime);
clearESP8266SerialBuffer();
}
//Basically same as sendESP8266Cmdln()
//But call ESP8266.print() instead of call ESP8266.println()
void sendESP8266Data(String data, int waitTime)
{
ESP8266.print(data);
delay(waitTime);
clearESP8266SerialBuffer();
}
//Clear and display Serial Buffer for ESP8266
void clearESP8266SerialBuffer()
{
Serial.println("= clearESP8266SerialBuffer() =");
while (ESP8266.available() > 0) {
char a = ESP8266.read();
Serial.write(a);
}
Serial.println("==============================");
}
NOTICE:
In my test, sometimes the ESP8266 ESP-12 reset and show the vendor website. It's caused by the pre-load old firmware, to fix it, flash ESP8266 with new firmware. Refer to my next exercise with the updated firmware 00200.9.5(b1).
To know the "+IPD" and the connection id, I prepare this simple program to show the incoming data on Serial Monitor, without response back to the client.
testDue8266Web.ino
/*
Arduino Due - ESP 8266 WiFi Module
Serial (Tx/Rx) communicate to PC via USB
Serial3 (Tx3/Rx3) connect to ESP8266
Tx3 - ESP8266 Rx
Rx3 - ESP8266 Tx
ESP8266 CH_PD Connect to ESP8266 VCC
*/
#define ASCII_0 48
#define ESP8266 Serial3
//String SSID = "TestAP";
//String PASSWORD = "12345678";
int LED = 13;
boolean FAIL_8266 = false;
String strHTML = "<!doctype html>\
<html>\
<head>\
<title>arduino-er</title>\
</head>\
<body>\
<H1>arduino-er.blogspot.com</H1>\
</body>\
</html>";
void setup() {
pinMode(LED, OUTPUT);
digitalWrite(LED, LOW);
delay(300);
digitalWrite(LED, HIGH);
delay(200);
digitalWrite(LED, LOW);
delay(300);
digitalWrite(LED, HIGH);
delay(200);
digitalWrite(LED, LOW);
delay(300);
digitalWrite(LED, HIGH);
delay(200);
digitalWrite(LED, LOW);
do{
Serial.begin(9600);
ESP8266.begin(9600);
//Wait Serial Monitor to start
while(!Serial);
Serial.println("--- Start ---");
ESP8266.println("AT+RST");
delay(1000);
if(ESP8266.find("ready"))
{
Serial.println("Module is ready");
ESP8266.println("AT+CWMODE=2");
delay(1000);
clearESP8266SerialBuffer();
sendESP8266Cmdln("AT+CIFSR", 1000);
//Set multi connections
sendESP8266Cmdln("AT+CIPMUX=1", 1000);
//Setup web server on port 80
sendESP8266Cmdln("AT+CIPSERVER=1,80",1000);
Serial.println("Server setup finish");
}else{
Serial.println("Module have no response.");
delay(500);
FAIL_8266 = true;
}
}while(FAIL_8266);
digitalWrite(LED, HIGH);
}
void loop(){
while (ESP8266.available() > 0) {
char a = ESP8266.read();
Serial.write(a);
}
}
boolean waitOKfromESP8266(int timeout)
{
do{
Serial.println("wait OK...");
delay(1000);
if(ESP8266.find("OK"))
{
return true;
}
}while((timeout--)>0);
return false;
}
//Send command to ESP8266, assume OK, no error check
//wait some time and display respond
void sendESP8266Cmdln(String cmd, int waitTime)
{
ESP8266.println(cmd);
delay(waitTime);
clearESP8266SerialBuffer();
}
//Basically same as sendESP8266Cmdln()
//But call ESP8266.print() instead of call ESP8266.println()
void sendESP8266Data(String data, int waitTime)
{
ESP8266.print(data);
delay(waitTime);
clearESP8266SerialBuffer();
}
//Clear and display Serial Buffer for ESP8266
void clearESP8266SerialBuffer()
{
Serial.println("= clearESP8266SerialBuffer() =");
while (ESP8266.available() > 0) {
char a = ESP8266.read();
Serial.write(a);
}
Serial.println("==============================");
}
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