Question

I have the following Arduino code. It connects to a server and sends the sensor’s readings to it. The reply from the server is always:

HTTP/1.1 400 Bad Request

The Arduino code is as follows.

#include <Ethernet.h>           //Library for Ethernet functions
#include <Client.h>             //Library for client functions
#include <OneWire.h>            //Library for the onewire bus
#include <SPI.h>

// Ethernet settings
uint8_t hwaddr[6]   = {0xDE, 0xAD, 0xBE, 0xEF, 0xBA, 0xBE}; // MAC address of Arduino
uint8_t ipaddr[4]   = {192, 168,   0, 55};                  // IP address of Arduino
uint8_t gwaddr[4]   = {192, 168,   0,  1};                  // IP address of gateway ( for later DNS implementation)
uint8_t subnet[4]   = {255, 255, 255,  0};                  // Subnet mask           ( for later DNS implementation)
uint8_t serverip[4] = {192, 168,   0, 54};                  // IP address of server arduino sends data to

uint8_t serverport = 80;                                    // The port the Arduino talks to

EthernetClient client;           // Make a new instance from type "Client" named "client", giving it
int numSensors;                  // a variable to store the number of sensors.

bool connected = false;          // Yes-no variable (boolean) to store if the arduino is connected to the server.
int i = 0;                       // Variable to count the sendings to the server.

void setup() {
    Serial.begin(9600);                                       // Start the serial port
    Serial.println("Initializing Ethernet.");
    Ethernet. begin(hwaddr, ipaddr);                          // Start up Ethernet
}

void loop() {
    if(!connected)   {                                        // If "not" connected print: not connected ;)
        Serial.println("Not connected");
        Serial.println("Connecting to server...");
        if (client.connect(serverip, serverport)) {           // If connected, set variable connected to "true" and
            connected = true;
            Serial.println("connected!!");
            String data;
            data+="";
            data+="t0=";
            data+=analogRead(A0);
            //    data+="&&";
            //    data+="t1=";
            //    data+=analogRead(A1);
            //    data+="&&";
            //    data+="t2=";
            //    data+=analogRead(A2);
            Serial.println("Sending to Server: ");
            Serial.println();
            client.print("GET /formSubmit.php?" + data);
            Serial.print("GET /formSubmit.php?" + data);
            client.println(" HTTP/1.1");
            Serial.println(" HTTP/1.1");
            client.println("Host: http://localhost/PhpProject1");
            Serial.println("Host: http://localhost/PhpProject1");
            client.println("User-Agent: Arduino");
            Serial.println("User-Agent: Arduino");
            client.print("Content-Length: ");
            Serial.print("Content-Length: ");
            client.println(data.length());
            Serial.println(data.length());
            client.println("Accept: text/html");
            Serial.println("Accept: text/html");
            client.println("Connection: close");
            Serial.println("Connection: close");

            client.println();
            Serial.println();

            if (client.available()) {
                char c = client.read();
                Serial.print(c);
            }
            delay(10000);
        }
        else {
            Serial.println("Cannot connect to Server");       //  else block if the server connection fails (debugging)
        }                                                     
    }                                                         
    else {                                                    
        delay(500);                                           //
        while (client.connected() && client.available()) {    // When connected and availabe:
            char c = client.read();                           // read the answer of the server and
            Serial.print(c);                                  // print it to serial port
        }
        //
        Serial.println();                                     //
        client.stop();                                        // Stop the connection and set
        connected = false;                                    // "connected" to false
    }
}

The output on the serial monitor after uploading this code is:

Initializing Ethernet.
Not connected

Connecting to server...
connected!!

Sending to Server:

GET /formSubmit.php?t0=433 HTTP/1.0
Host: http://localhost/PhpProject1
User-Agent: Arduino
Content-Length: 6
Accept: text/html
Connection: close



HTTP/1.1 400 Bad Request
Date: Sat, 03 Nov 2012 17:06:00 GMT
Server: Apache/2.4.3 (Win32) OpenSSL/1.0.1c PHP/5.4.7
Content-Length: 343
Connection: close
Content-Type: text/html; charset=iso-8859-1

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>400 Bad Request</title>
</head><body>
<h1>Bad Request</h1>
<p>Your browser sent a request that this server could not understand.<br />
</p>
<hr>
<address>Apache/2.4.3 (Win32) OpenSSL/1.0.1c PHP/5.4.7 Server at http://localhost/PhpProject1 Port 80</address>
</body></html>

What might be the problem?

Answer 1

You request is bad.

1. Host field must not contain /, try: Host: localhost
2. Content-Length make no sense in GET method
3. Maybe you need to terminate each lines by \r\n instead of just \n (depending on server)