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== Survey (Everybody Votes)

image::survey.png[Everybody Votes]

The surveyor pattern is used to send a timed survey out, responses
are individually returned until the survey has expired.  This pattern
is useful for service discovery and voting algorithms.

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

.Compilation
[source,bash]
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gcc survey.c -lnanomosg -o survey
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.Execution
[source,bash]
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./survey server ipc:///tmp/survey.ipc & server=$!
./survey client ipc:///tmp/survey.ipc client0 & client0=$!
./survey client ipc:///tmp/survey.ipc client1 & client1=$!
./survey client ipc:///tmp/survey.ipc client2 & client2=$!
sleep 4 <1>
kill $server $client0 $client1 $client2
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<1> The first survey times out with no responders because the clients aren’t started yet.

.Output
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SERVER: SENDING DATE SURVEY REQUEST
SERVER: SURVEY COMPLETE
SERVER: SENDING DATE SURVEY REQUEST
CLIENT (client2): RECEIVED "DATE" SURVEY REQUEST
CLIENT (client1): RECEIVED "DATE" SURVEY REQUEST
CLIENT (client0): RECEIVED "DATE" SURVEY REQUEST
CLIENT (client1): SENDING DATE SURVEY RESPONSE
CLIENT (client0): SENDING DATE SURVEY RESPONSE
CLIENT (client2): SENDING DATE SURVEY RESPONSE
SERVER: RECEIVED "Mon Jan  8 13:10:43 2018" SURVEY RESPONSE
SERVER: RECEIVED "Mon Jan  8 13:10:43 2018" SURVEY RESPONSE
SERVER: RECEIVED "Mon Jan  8 13:10:43 2018" SURVEY RESPONSE
SERVER: SURVEY COMPLETE
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