Hello!
I have a hard time getting a webserver work with both AJAX and fileserver (send .csv data).
Problem is, when the .csv file is availale, the browser do not open, it ask for option to "download". I can not use the "download" as my .csv reciver refuse the connection. And, when I ask for the .csv file, the AJAX function stop. When I try to open index.htm after the .csv request it refuse to open index.htm.
I think the problem is in the http header coding. But I have a hard time understand how to make these two function work together. Anyone out there with knowhow that can help me? 
The AJAX server code, from: https://startingelectronics.org/tutorials/arduino/ethernet-shield-web-server-tutorial/SD-card-IO/
/*--------------------------------------------------------------
Program: eth_websrv_SD_Ajax_in_out
Description: Arduino web server that displays 4 analog inputs,
the state of 3 switches and controls 4 outputs,
2 using checkboxes and 2 using buttons.
The web page is stored on the micro SD card.
Hardware: Arduino Uno and official Arduino Ethernet
shield. Should work with other Arduinos and
compatible Ethernet shields.
2Gb micro SD card formatted FAT16.
A2 to A4 analog inputs, pins 2, 3 and 5 for
the switches, pins 6 to 9 as outputs (LEDs).
Software: Developed using Arduino 1.0.5 software
Should be compatible with Arduino 1.0 +
SD card contains web page called index.htm
References: - WebServer example by David A. Mellis and
modified by Tom Igoe
- SD card examples by David A. Mellis and
Tom Igoe
- Ethernet library documentation:
http://arduino.cc/en/Reference/Ethernet
- SD Card library documentation:
http://arduino.cc/en/Reference/SD
Date: 4 April 2013
Modified: 19 June 2013
- removed use of the String class
Author: W.A. Smith, http://startingelectronics.com
--------------------------------------------------------------*/
#include <SPI.h>
#include <Ethernet.h>
#include <SD.h>
// size of buffer used to capture HTTP requests
#define REQ_BUF_SZ 60
// MAC address from Ethernet shield sticker under board
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress ip(192, 168, 10, 20); // IP address, may need to change depending on network
EthernetServer server(80); // create a server at port 80
File webFile; // the web page file on the SD card
File webFile2; // the web page file on the SD card
File webFile3; // the web page file on the SD card
char HTTP_req[REQ_BUF_SZ] = {0}; // buffered HTTP request stored as null terminated string
char req_index = 0; // index into HTTP_req buffer
boolean LED_state[4] = {0}; // stores the states of the LEDs
void setup()
{
// disable Ethernet chip
pinMode(10, OUTPUT);
digitalWrite(10, HIGH);
Serial.begin(9600); // for debugging
// initialize SD card
Serial.println("Initializing SD card...");
if (!SD.begin(4)) {
Serial.println("ERROR - SD card initialization failed!");
return; // init failed
}
Serial.println("SUCCESS - SD card initialized.");
// check for index.htm file
if (!SD.exists("index.htm")) {
Serial.println("ERROR - Can't find index.htm file!");
return; // can't find index file
}
Serial.println("SUCCESS - Found index.htm file.");
// switches on pins 2, 3 and 5
pinMode(2, INPUT);
pinMode(3, INPUT);
pinMode(5, INPUT);
// LEDs
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);
Ethernet.begin(mac, ip); // initialize Ethernet device
server.begin(); // start to listen for clients
}
void loop()
{
EthernetClient client = server.available(); // try to get client
if (client) { // got client?
boolean currentLineIsBlank = true;
while (client.connected()) {
if (client.available()) { // client data available to read
char c = client.read(); // read 1 byte (character) from client
// limit the size of the stored received HTTP request
// buffer first part of HTTP request in HTTP_req array (string)
// leave last element in array as 0 to null terminate string (REQ_BUF_SZ - 1)
if (req_index < (REQ_BUF_SZ - 1)) {
HTTP_req[req_index] = c; // save HTTP request character
req_index++;
}
// last line of client request is blank and ends with \n
// respond to client only after last line received
if (c == '\n' && currentLineIsBlank) {
// send a standard http response header
client.println("HTTP/1.1 200 OK");
// remainder of header follows below, depending on if
// web page or XML page is requested
// Ajax request - send XML file
if (StrContains(HTTP_req, "ajax_inputs")) {
// send rest of HTTP header
client.println("Content-Type: text/xml");
client.println("Connection: keep-alive");
client.println();
SetLEDs();
// send XML file containing input states
XML_response(client);
}
else { // web page request
// send rest of HTTP header
client.println("Content-Type: text/html");
client.println("Connection: keep-alive");
client.println();
// send web page
webFile = SD.open("index.htm"); // open web page file
if (webFile) {
while(webFile.available()) {
client.write(webFile.read()); // send web page to client
}
webFile.close();
}
}
// display received HTTP request on serial port
// Serial.print(HTTP_req);
// reset buffer index and all buffer elements to 0
req_index = 0;
StrClear(HTTP_req, REQ_BUF_SZ);
break;
}
// every line of text received from the client ends with \r\n
if (c == '\n') {
// last character on line of received text
// starting new line with next character read
currentLineIsBlank = true;
}
else if (c != '\r') {
// a text character was received from client
currentLineIsBlank = false;
}
else if (StrContains(HTTP_req, "GET /DATA.CSV")) {
webFile2 = SD.open("/DATA.CSV");
if (webFile2) {
client.println("HTTP/1.1 200 OK");
client.println();
}
}
File webFile2 = SD.open("/DATA.CSV",FILE_READ);
while(webFile2.available()) {
int num_bytes_read;
uint8_t byte_buffer[32];
num_bytes_read=webFile2.read(byte_buffer,32);
client.write(byte_buffer,num_bytes_read);
}
webFile2.close();
delay(1); // give the web browser time to receive the data
client.stop(); // close the connection
} // end if (client.available())
} // end while (client.connected())
delay(1); // give the web browser time to receive the data
client.stop(); // close the connection
} // end if (client)
}
// checks if received HTTP request is switching on/off LEDs
// also saves the state of the LEDs AA: Setter digital utgang med checkboks/ny slider?
void SetLEDs(void)
{
// LED 1 (pin 6)
if (StrContains(HTTP_req, "LED1=1")) {
LED_state[0] = 1; // save LED state
digitalWrite(6, HIGH);
Serial.print("DO6 høy, led1");
}
else if (StrContains(HTTP_req, "LED1=0")) {
LED_state[0] = 0; // save LED state
digitalWrite(6, LOW);
Serial.print("DO6 lav, led 1");
}
// LED 2 (pin 7)
if (StrContains(HTTP_req, "LED2=1")) {
LED_state[1] = 1; // save LED state
digitalWrite(7, HIGH);
Serial.print("DO7 høy, led 2");
}
else if (StrContains(HTTP_req, "LED2=0")) {
LED_state[1] = 0; // save LED state
digitalWrite(7, LOW);
Serial.print("DO7 lav, led2");
}
// LED 3 (pin 8)
if (StrContains(HTTP_req, "LED3=1")) {
LED_state[2] = 1; // save LED state
digitalWrite(8, HIGH);
Serial.print("DO8 høy, led3");
}
else if (StrContains(HTTP_req, "LED3=0")) {
LED_state[2] = 0; // save LED state
digitalWrite(8, LOW);
Serial.print("DO8 lav, led3");
}
// LED 4 (pin 9)
if (StrContains(HTTP_req, "LED4=1")) {
LED_state[3] = 1; // save LED state
digitalWrite(9, HIGH);
Serial.print("DO9 høy, led4");
}
else if (StrContains(HTTP_req, "LED4=0")) {
LED_state[3] = 0; // save LED state
digitalWrite(9, LOW);
Serial.print("DO9 lav, led4");
}
}
// send the XML file with analog values, switch status AA BINARY INPUT status
// and LED status
void XML_response(EthernetClient cl)
{
int analog_val; // stores value read from analog inputs
int count; // used by 'for' loops
int sw_arr[] = {2, 3, 5}; // pins interfaced to switches
cl.print("<?xml version = \"1.0\" ?>");
cl.print("<inputs>");
// read analog inputs
for (count = 2; count <= 5; count++) { // A2 to A5
analog_val = analogRead(count);
cl.print("<analog>");
cl.print(analog_val);
cl.println("</analog>");
}
// read switches AA SWITCH ER ALTSÅ BINARY INPUT....
for (count = 0; count < 3; count++) {
cl.print("<switch>");
if (digitalRead(sw_arr[count])) {
cl.print("ON");
}
else {
cl.print("OFF");
}
cl.println("</switch>");
}
// checkbox LED states AA SENDER TEKST TIL Å STÅ VEDSIDEN AV "SWITCH INPUTS" SOM ER BINÆR INNGANG, ON eller OFF
// LED1
cl.print("<LED>");
if (LED_state[0]) {
cl.print("checked");
}
else {
cl.print("unchecked");
}
cl.println("</LED>");
// LED2
cl.print("<LED>");
if (LED_state[1]) {
cl.print("checked");
}
else {
cl.print("unchecked");
}
cl.println("</LED>");
// button LED states
// LED3
cl.print("<LED>");
if (LED_state[2]) {
cl.print("on");
}
else {
cl.print("off");
}
cl.println("</LED>");
// LED4
cl.print("<LED>");
if (LED_state[3]) {
cl.print("on");
}
else {
cl.print("off");
}
cl.println("</LED>");
cl.print("</inputs>");
}
// sets every element of str to 0 (clears array)
void StrClear(char *str, char length)
{
for (int i = 0; i < length; i++) {
str[i] = 0;
}
}
// searches for the string sfind in the string str
// returns 1 if string found
// returns 0 if string not found
char StrContains(char *str, char *sfind)
{
char found = 0;
char index = 0;
char len;
len = strlen(str);
if (strlen(sfind) > len) {
return 0;
}
while (index < len) {
if (str[index] == sfind[found]) {
found++;
if (strlen(sfind) == found) {
return 1;
}
}
else {
found = 0;
}
index++;
}
return 0;
}