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== Request/Reply (I ask, you answer)

image::reqrep.png[I ask, you answer]

Request/Reply is used for synchronous communications where each question
is responded with a single answer, for example remote procedure calls (RPCs).
Like <<pipeline#,Pipeline>>, it also can perform load-balancing.  This
is the only reliaable messaging pattern in the suite, as it automatically
will retry if a request is not matched with a response.

.reqprep.c
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include::src/reqrep.c[]
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<1> Blithely assumes message is ASCIIZ string. Real code should check it.

.Compilation
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gcc reqrep.c -lnanomsg -o reqrep
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.Execution
[source,bash]
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./reqrep node0 ipc:///tmp/reqrep.ipc & node0=$! && sleep 1
./reqrep node1 ipc:///tmp/reqrep.ipc
kill $node0
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.Output
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NODE1: SENDING DATE REQUEST DATE
NODE0: RECEIVED DATE REQUEST
NODE0: SENDING DATE Sat Sep  7 17:39:01 2013
NODE1: RECEIVED DATE Sat Sep  7 17:39:01 2013
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