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