Arduino WiFi shield post with header problems - post

Question

I'm trying to do a post from the arduino wifi shield to my java servlet. The servlet functions with url get, and jquery post, but I can't sort the headers out in my arduino code. Any help will be greatly appreciated!
The server returns 200, but I'm not getting the payload "content" as value. I'm not exactly sure what I'm doing wrong but I'm pretty sure it's in how my headers are setup. I've spent the last two days trying to get it.
#include <SPI.h>
#include <WiFi.h>
char ssid[] = "jesussavesforjust19.95"; // your network SSID (name)
char pass[] = "********"; // your network password (use for WPA, or use as key for WEP)
int keyIndex = 0; // your network key Index number (needed only for WEP)
int status = WL_IDLE_STATUS;
IPAddress server(192,168,10,149); // numeric IP for Google (no DNS)
WiFiClient client;
void setup() {
Serial.begin(9600);
// attempt to connect to Wifi network:
while ( status != WL_CONNECTED) {
Serial.println("Attempting to connect to SSID: ");
Serial.println(ssid);
status = WiFi.begin(ssid, pass);
// wait 10 seconds for connection:
delay(10000);
}
Serial.println("Connected to wifi");
printWifiStatus();
sendData("0600890876");
}
void loop() {
// if there's incoming data from the net connection.
// send it out the serial port. This is for debugging
// purposes only:
if (client.available()) {
char c = client.read();
Serial.println(c);
}
//String dataString = "060088765";
// if you're not connected, and ten seconds have passed since
// your last connection, then connect again and send data:
if(!client.connected())
{
Serial.println();
Serial.println("disconnecting.");
client.stop();
//sendData(dataString);
for(;;)
;
}
}
// this method makes a HTTP connection to the server:
void sendData(String thisData) {
// if there's a successful connection:
Serial.println("send data");
if (client.connect(server, 8080)) {
String content = "value=0600887654";
Serial.println(content);
Serial.println("connected");
client.println("POST /hos HTTP/1.1");
client.println("Host:localhost");
client.println("Connection:Keep-Alive");
client.println("Cache-Control:max-age=0");
client.println("Content-Type: application/x-www-form-urlencoded\n");
client.println("Content-Length: ");
client.println(content.length());
client.println("\n\n");
client.println(content);
}
else {
// if you couldn't make a connection:
Serial.println("form connection failed");
Serial.println();
Serial.println("disconnecting.");
client.stop();
}
}
void printWifiStatus() {
// print the SSID of the network you're attached to:
Serial.println("SSID: ");
Serial.println(WiFi.SSID());
// print your WiFi shield's IP address:
IPAddress ip = WiFi.localIP();
Serial.println("IP Address: ");
Serial.println(ip);
// print the received signal strength:
long rssi = WiFi.RSSI();
Serial.println("signal strength (RSSI):");
Serial.println(rssi);
Serial.println(" dBm");
}

Answer 1

Perhaps, some of your "Serial.println" and "client.println" commands should be "Serial.print" and "client.print" instead. For example:
client.print("Content-Length: ");
client.println(content.length());
would avoid adding a line break between the text and the number.

Answer 2

This is maybe more advice on an approach than an answer.
If I was doing something like this I would not start on the Arduino. The endless compile, download, run, look at print()'s would drive me crazy. I would fully prototype the client/server interaction in whatever you have at your fingertips, preferably something with a debugger. (Java, Python, PHP, VB, whatever you know that you can slap together)
Second, I would run Wireshark on the server so that I could see exactly what was being sent and responded.
Then I would port the same interaction over to the Arduino. Again inspect with Wireshark to confirm you are getting what you expected. If you send the same bytes, you should get the same response.
Even if you choose to implement straight on Arduino, consider having Wireshark to capture the actual network traffic.
With Wireshark, you might see that the Arduino println() is not sending the correct line end for the server.
Also, there is no guarantee that last println() is actually sent. The network stack implementation is free to buffer as it sees fit. You might need a flush(). A packet trace would show this.
With a packet capture you might find that time matters. In theory TCP is a stream and you should be able to send that POST data 1 character at a time in 1 packet and everything would work. But the Arduino might be so slow executing those println()'s by the server's standards that it times out. In such case you would see the server respond before the Arduino even finished sending.