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9. Ethernet protocol specification
The main purpose of the Ethernet connection is to collect measurement data from the
refractometer. For this data acquisition, you’ll need to have suitable software on your
computer. You can program a data acquisition program yourself following the specifications
below.
For examples and ready-made applications, contact Vaisala.
9.1 Communication protocol
The communications protocol is based on UDP/IP to port 50023 . It is a client/server protocol,
where the refractometer is the server and thus only sends information when the client (your
computer) requests it. The server should answer to all requests within 100 ms.
9.1.1 Request format
The client to server communication, i.e. the requests sent from your computer to the
refractometer, is in binary format. The request packets contain the following binary data (all
integers are in the network order, MSB first):
• 32-bit integer: packet number
• 32-bit integer: request ID
• (any): request data (depends on the request)
• (any): fill-indata
The maximum size of the message is 1472 octets(bytes).
The packet number is echoed back by the refractometer, but not processed in any way.
The packet numbers do not have to be sequential, any 32-bit value is valid.
The request ID is a 32-bit value that identifies the requested function, for example
refractometer information. See Request-response pair specification (page 38) for request IDs.
The request data consists of 0 to 1464 octets of additional data associated with the request.
The fill-indata can be used to increase the number of octets in a message. Any number of
NULL characters (0x00) may be added to the end of the request as long as the total size of
the message does not exceed the maximum of 1472 octets. This may be useful, for example, if
the client implementation uses fixed-length packets.
9.1.2 Response format
The response data sent by the refractometer is in ASCII format. With the exception of the
packet number, the data is human-readable. The data structure is very simple:
Chapter 9 – Ethernet protocol specification
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