= reqrep
This is a very simple RPC service using the REQ/REP method.
It is derived in part from Tim Dysinger's
http://nanomsg.org/gettingstarted/[Getting Started With Nanomsg]
examples, but we have updated for _nng_, and converted to use binary
frames across the wire instead of string data.
The protocol is simple:
* Client will send a 64-bit command (network byte order, i.e. big endian).
* Server sends a 64-bit response (also network byte order.)
The only command is "DATE", which has value 0x1. The value returned is
a UNIX timestamp (seconds since Jan 1, 1970.)
(We used 64-bit values for simplicity, and to avoid the Y2038 bug when
compiled on 64-bit systems.)
== Compiling
CMake with ninja-build is simplest:
[source, bash]
----
% mkdir build
% cd build
% cmake -G Ninja ..
% ninja
----
Or if you prefer a traditional approach,
the following is an example typical of UNIX and similar systems like
Linux and macOS may appeal:
[source, bash]
----
% export CPPFLAGS="-I /usr/local/include"
% export LDFLAGS="-L /usr/local/lib -lnng"
% export CC="cc"
% ${CC} ${CPPFLAGS} reqrep.c -o reqrep ${LDFLAGS}
----
== Running
You can run either the client or the server, and use whatever legal
_nng_ URL you like:
[source, bash]
----
% ./reqrep server tcp://127.0.0.1:8899 &
% ./reqrep client tcp://127.0.0.1:8899
CLIENT: SENDING DATE REQUEST
SERVER: RECEIVED DATE REQUEST
SERVER: SENDING DATE: Thu Feb 8 10:26:18 2018
CLIENT: RECEIVED DATE: Thu Feb 8 10:26:18 2018
----
