Microsoft KB Archive/22448

Information Concerning ETX/ACK Protocol

PSS ID Number: Q22448 Article last modified on 11-02-1994

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MS-DOS

Question:

What is ETX/ACK?

Response:

ETX/ACK is a serial communication software handshaking protocol for controlling the flow of data from the transmitter (e.g. computer) to the receiver (e.g. printer). This control is necessary to ensure that the transmitter sends data only when the receiver is able to process the data.

In ETX/ACK the transmitter divides the data into blocks of a certain size. The transmitter decides what the size of the blocks is. Thus, with ETX/ACK the transmitter is in control of the protocol, and the transmitter is responsible for sending blocks of data of a size that the receiver can handle. At the end of a block of data, the transmitter sends the ETX (End Of Text) character (ASCII decimal 3). When the receiver receives the ETX character, it sends the ACK (Acknowledge) character (ASCII decimal 6) back to the transmitter to let it know that it has received the chunk of data and is ready for the next one. The transmitter then sends the next block of data, and so on.

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================================================================ Copyright Microsoft Corporation 1994.