Vaisala RVP900

Chapter 3 _______________________________________________________ Hardware Installation
VAISALA_______________________________________________________________________ 83
3.3.4.3 Socket Protocol
The socket interface basically supports all the "Host Computer
Commands" in Chapter 7, Host Computer Commands, on page 255. There
are a few layers of formatting on top of that. All messages going both ways
consist at the lowest level of an 8-character decimal ASCII number,
followed by a block of data. The decimal number indicates how many
bytes follow. Generally, all data transfers are initiated by the host computer
by sending a block of data, which consists of a command word followed
by the "|" character, followed by optional data.
It responds to all commands with either an "Ack|", indicating
acknowledgment that the command was OK, or "Nak|", indicating that
there was an error. For Nak, the reply always includes a string indicating
what the error was. For Ack, there is optional data following.
On initial socket connection request DspExport provides a response of
either Nak, indicating the connection failed and why, or Ack, followed by
some connection information. This Ack string is in the form of name/value
pairs, and looks something to:
Ack|CanCompress=1,Model=RVP900,Version=7.32
Your program can choose to evaluate, or ignore, any of these keywords.
"CanCompress=1" indicates that the DspExport computer supports
compression. The host computer can then choose to use compression if it
wants to. When you first connect, you are in the "info only" mode. This
means that the server only responds to INFO and OPEN commands.
DspExport supports only the six commands:
- Read Command (READ)
- Write Command (WRIT)
- Read Status Command (STAT)
- Set Information Command (INFO)
- Read data available command (RDAV)
- Open the connection for I/O (OPEN)
3.3.4.3.1 Read Command (READ)
Example: "READ|100|" means read 100 bytes from the RVP900. Since the
RVP900 interface is a 16-bit word interface, these read sizes should always
be even. It always replies with a "Ack|" followed by 100 bytes of binary
data, or with a "Nak|"; in other words there can be no partial reads.