Transmission Mechanism

Understanding the Transmission Mechanism

When working with the myPOS payment protocol, the terminal acts as a server. Communication is handled as a single-threaded, asynchronous process. Even if the terminal can accept multiple connections, it will respond with BUSY if it is already processing a transaction.

A transaction starts when the terminal approves a request and responds with STAGE = 1, STATUS = 0, and ends when the terminal responds with STAGE = 5.

Typical request flow:

1. Connect to the terminal.
2. Send your request.
3. Receive an answer with STAGE = 1.
   • If STATUS = 0, wait for the next answer.
4. Continue receiving responses until you get STAGE = 5.
5. Close the connection.

• It is recommended to wait up to 5 seconds for the answer with STAGE = 1.
• Timeouts for the next stages will be specified in the previous response.

Transaction Process

The transaction process follows the above communication pattern, ensuring that each transaction is handled one at a time and responses are received in the correct order.

Communication Modes

Depending on the POS device configuration, the terminal can communicate in different modes:

• Cash Register Mode:
  The device uses its own connection to the Acquirer HOST to process transactions. This is the default mode described in this documentation.

• Slave Mode:
  The device uses the caller's (host system's) connectivity to send data to and receive responses from the Acquirer HOST.