Arduino以太网屏蔽-对服务器的GET请求无响应

Question

I have a code for the Arduino Ethernet Shield that will send a GET request to a server and return a PHP echo statement.

However, most of the time it fails to connect to the server.

When it does connect, I keep getting 403 Forbidden error or it says bad header format for "Host:".

I have checked every forum and all StackOverflow links related to the topic, but none of their solutions worked. My code is attached below.

#include <SPI.h>
#include <Ethernet.h>

byte mac[] = {0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
char server[] = "kanishkaganguly.byethost5.com";
IPAddress ip(192,168,0,103);

EthernetClient client;

void setup() {
 Serial.begin(9600);
 while (!Serial) {
    ;
 }

 Ethernet.begin(mac, ip);

 delay(1000);
 Serial.println("connecting...");

 if (client.connect(server, 80)) {
    Serial.println("connected");
    client.println("GET /test.php HTTP/1.1");
    client.println("Host: www.arduino.cc");
    client.println("User-Agent: arduino-ethernet");
    //client.println("User-Agent: Mozilla/5.0"); 
    //This supposedly fixed 403 error for another user
    client.println("Connection: close");
    client.println();
 }else {
    Serial.println("connection failed");
 }
}

void loop(){
  // if there are incoming bytes available 
  // from the server, read them and print them:
   if (client.available()) {
     char c = client.read();    
     Serial.print(c);
   }

  // if the server's disconnected, stop the client:
  if (!client.connected()) {
     Serial.println();
     Serial.println("disconnecting.");
     client.stop();

     // do nothing forevermore:
     for(;;)     ;  
   }
 }

Answer 1

I figured out the problem. The client.println() as a new line isn't working for some reason. So, here is the updated code

client.print("GET /checkcontrol.php HTTP/1.1\r\n");
client.print("Host: shahz.webatu.com\r\n");
client.print("User-Agent: arduino-ethernet\r\n");
client.print("Connection: close\r\n\r\n");

The \\r\\n is the right way to go about adding a new line for the server to recognize.

Answer 2

The Host header specifies the hostname of the site you're connecting to. In this case, you are trying to connect to the domain kanishkaganguly.byethost5.com , but your Host header is set to www.arduino.cc . Usually this is incorrect. The Host header should match the domain, so both should be kanishkaganguly.byethost5.com .

When a client connects to a domain, the client first resolves the domain name to an IP, then makes the connection to that IP. Because the connection is made to the IP, the server does not know what domain name was looked up by the client. Because IPs are a limited resource, many hosting providers host multiple domains on a single IP. Without the Host header, the server would not know which page to return to the client.

Answer 3

The println command sends the text followed by "\\r\\n" so instead of changing every println for print, you could have added CRLF to the close line.

Client.println("Connection: close\\r\\n")