 <p>I somewhat got it to work using some of the existing code above, but it is still not optimal. This might be useful for others.</p> <p>This is what I did:</p> <p>1) I socket dial only once (during initialization)</p> <p>2) The POST-section is running inside a loop infinitely. The 5 second delay is now reduced to 200 ms and I added some headers, like so:</p> <pre><code> //unsigned long data = random(1000000000000000, 9999999999999999); LTESerial.print("POST /index.php?data="); LTESerial.print(data); LTESerial.print(" HTTP/1.1\r\n"); LTESerial.print("Host: ADDRESS\r\n"); LTESerial.print("Connection: keep-alive\r\n\r\n"); delay(200); while (getResponse() &gt; 0); </code></pre> <p>3) Turns out my WAMP server (PHP) had limitations as default in terms of maximum HTTP requests, timeouts and the like. I had to increase these numbers (I changed them to unlimited) inside <code>php.ini</code>.</p> <p>However, while I am able to "continuously" send data to my server, a delay of 200 ms is still a lot. I would like to see something close to serial communication, if possible.</p> <p>Also, when looking at the serial monitor, I get:</p> <pre><code>[...] 408295030 4238727231 3091191349 2815507344 -----------&gt;(THEN SUDDENLY)&lt;------------ HTTP/1.1 200 OK Date: Thu, 02 Jun 2 2900442411 016 19:29:41 GMT Server: Apache/2.4.17 (Win32) PHP/5.6.15 X-P16 3817418772 Keep-Alive: timeout=5 Connection: Keep-Alive Content-Type: te 86026031 HTTP/1.1 200 OK Date: Thu, 02 Jun 2016 19:29:4 3139838298 75272508 [...] -----------&gt;(After 330 iterations/POSTs, I get)&lt;------------ NO CARRIER NO CARRIER NO CARRIER NO CARRIER </code></pre> <p>So my question is: 1) How do I eliminate the 200 ms delay as well?</p> <p>2) If my data-points have different sizes, the delay will have to change as well. How to do this dynamically?</p> <p>3) Why does it stop at 330-ish iterations? This doesn't happen if data is only 4 digits.</p> <p>4) Why do I suddenly get responses from the server?</p> <p>I hope someone can use this for their own project, however this does not suffice for mine. Any ideas?</p>