The hard part was finding Comcast XFINITY remote codes. My remote is an XR11. This took a lot of digging and signal code converting, but I eventually ended up with the RAW IR codes for each button on the XFINITY XR11 remote.

The HTTP IR Blaster uses a URL format like this:

http://10.0.0.10:8081/json?pass=my_password&plain=[{"type":"raw","data":[100,200,300,etc.],"khz":38,"pulse":1}]

Except, the "data" part has many many more numbers. And, if you want to send a few numbers to send a channel code to your X1 box, you'll need more than one {} object in the string, separated by comma's. Here's an example of a 3-channel code, plus the OK button to tell the blaster to change to channel 810. The data in the brackets after &plain= is formatted like this:

[{code_for_number_8},{code_for_number_1},{code_for_number_0},{code_for_OK_button}]

Each button code needs the type (always "raw"), the data (different for each button), the frequency (always 38khz) and the pulse (always 1), so it looks like this:

{"type":"raw","data":[button_code],"khz":38,"pulse":1}

Now that you understand the format for sending channel codes to the X1, here are the button codes:

OK Button

[210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,1848,210,760,210,760,210,1032,210,1440,210,760,210,760,210,80400,210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,760,210,1848,210,760,210,1032,210,1440,210,760,210,760,210,80400]

Exit Button

[210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,1168,210,760,210,760,210,1032,210,2120,210,760,210,760,210,80400,210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,2256,210,1848,210,760,210,1032,210,2120,210,760,210,760,210,80400]

1:[210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,2664,210,760,210,760,210,760,210,896,210,760,210,760,210,80400,210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,1576,210,1848,210,760,210,760,210,896,210,760,210,760,210,80400]

2:

[210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,2528,210,760,210,760,210,760,210,1032,210,760,210,760,210,80400,210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,1440,210,1848,210,760,210,760,210,1032,210,760,210,760,210,80400]

3: [210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,2392,210,760,210,760,210,760,210,1168,210,760,210,760,210,80400,210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,1304,210,1848,210,760,210,760,210,1168,210,760,210,760,210,80400]

4: [210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,2256,210,760,210,760,210,760,210,1304,210,760,210,760,210,80400,210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,1168,210,1848,210,760,210,760,210,1304,210,760,210,760,210,80400]

5: [210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,2120,210,760,210,760,210,760,210,1440,210,760,210,760,210,80400,210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,1032,210,1848,210,760,210,760,210,1440,210,760,210,760,210,80400]

6: [210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,1984,210,760,210,760,210,760,210,1576,210,760,210,760,210,80400,210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,896,210,1848,210,760,210,760,210,1576,210,760,210,760,210,80400]

7: [210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,1848,210,760,210,760,210,760,210,1712,210,760,210,760,210,80400,210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,760,210,1848,210,760,210,760,210,1712,210,760,210,760,210,80400]

8: [210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,1712,210,760,210,760,210,760,210,1848,210,760,210,760,210,80400,210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,2800,210,1848,210,760,210,760,210,1848,210,760,210,760,210,80400]

9: [210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,1576,210,760,210,760,210,760,210,1984,210,760,210,760,210,80400,210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,2664,210,1848,210,760,210,760,210,1984,210,760,210,760,210,80400]

0: [210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,2800,210,760,210,760,210,760,210,760,210,760,210,760,210,80400,210,896,210,1712,210,760,210,2800,210,1304,210,1304,210,1168,210,2664,210,13800,210,896,210,1712,210,1848,210,760,210,760,210,760,210,760,210,760,210,80400]

Now, let's create an IFTTT command to send a channel code to the ESP8266.