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Create 2 POSIX named pipes:
- REQ_PIPE, used to send requests.
- REPLY_PIPE, used to get replies to the requests.
Open the pipes:
- REQ_PIPE as write_only.
- REPLY_PIPE as read_only.
Open the POSIX named message queue in write_only mode.
Send a message to this queue with the following format:
{
'C',
char req_pipe_name[255],
char reply_pipe_name[255]
}
Read from the reply pipe name, with a timeout. When the server has handled
your connection request, you will receive "ZoO_protocol_version X\n",
with X a positive integer indicating the version of the protocol. If you do
not support this protocol, proceed to destroying all the pipes, otherwise you
are now able to send requests.
Disconnecting is done by destroying the pipes. This goes both way: if you did
not initiate the destroying, assume that the server went offline.
Once connected, send your request on REQ_PIPE using the "CMD STRING\n" format,
in which:
- CMD is one of:
- "L" -> Learn STRING, do not reply, do not add to storage.
- "LS" -> Learn STRING, do not reply, add to storage.
- "LSR" -> Learn STRING, reply, add to storage.
- "R" -> Do not learn STRING, reply, do not add to storage.
- STRING must not contain the '\n' character.
The reply will come from REPLY_PIPE, using the "TYPE STRING\n" format, in which:
- TYPE is one of:
- "E" -> STRING contains an error message.
- "D" -> STRING contains the requested data.
- "C" -> All replies related to the request have been sent.
At most one "D" reply per request, exactly one "C" reply per request, any
number of "E" replies per request.
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