Troubleshooting SMS over IP


I am trying to use the low-level TCP/IP SMS-over-IP functionality with my Konekt SIM. I can make normal HTTP requests and I have independently tested the TCP connection using ngrok, so I think the network connection itself is OK.

I am opening a TCP connection, sending the string “SXXXXYYYY+447999123456 Test SMS\n\n”, where:
XXXX is my four-character ID
YYYY is my four-character key
+44 is the UK country code
7999123456 is the destination mobile number with leading zero removed
Test SMS is the actual message
\n\n is two newlines as specified in the API documentation.

I’m not receiving anything on the destination mobile. Can anyone suggest what I’m doing wrong?



Hey @jamesfowkes,

Are you sending that string with a space before + or without a space before +?


Without a space, the documentation doesn’t specify one. I’ll try with one later if that’s the issue.

Adding the space didn’t change anything. Just to clarify, I am doing the following:

  1. Opening a TCP connection to port 9999
  2. Sending the string
  3. Waiting for 2-byte reply
  4. Closing connection

The destination phone doesn’t receive anything and I don’t receive a reply over the TCP connection at step 3.
I’m using an Arduino Uno with a SIM800H board. The software debugging outputs says that the TCP connection is being made and that the data is being sent.

Does this look correct? I’m aiming to get a Konekt SIM working from as low resource a controller as possible, so having being able to use the TCP connection is important.

I’m having the same problem. I contacted Hologram support and they’re looking into it. In the meantime, did you manage to get this to work?