reqrep

This is a very simple RPC service using the REQ/REP method. It is derived in part from Tim Dysinger’s 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:

% 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:

% 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:

% ./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