There are different types of messages:

• Ping / Pong
• Write upstream
• Write downstream
• Read upstream
• Read downstream

When a device sends a message to the server, the server responds in the following way:

• Version: X
• Action: PING
• Content: []

• Version: X
• Action: WRITE_UP
• Content: [name, type, value]

• Version: X
• Action: READ_UP
• Content: [XXX]

• Version: X
• Action: PONG
• Content: []

• Version: X
• Action: WRITE_DOWN
• Content: [XXX]

• Version: X
• Action: READ_DOWN
• Content: [XXX]

/api/hexified(md5sum(hexified(device_id)))/

• device_id - The device id represented as RAW bytes.
• hexified - A string-friendly hex representation where each byte is represented in hex.
• md5sum - The md5sum of the input.

The payload of a packet is constructed as follows:

1. The version, action and payload length is added to the first x bytes.
2. The data content is appended
3. Pad bytes are appended, since AES requires input to be in block size of X (16 for AES128).
4. The device Id is appended (as raw bytes)
5. Payload is encrypted with AES128
6. The iv used for encryption is appended

AES128( version + action + len + content + device_id ) + iv