# nn_reqrep(7) Manual Page

## NAME

nn_reqrep - request/reply scalability protocol

## SYNOPSIS

#include <nanomsg/nn.h>

#include <nanomsg/reqrep.h>

## DESCRIPTION

This protocol is used to distribute the workload among multiple stateless workers.

Please note that request/reply applications should be stateless.

It’s important to include all the information necessary to process the request in the request itself, including information about the sender or the originator of the request if this is necessary to respond to the request.

Sender information cannot be retrieved from the underlying socket connection since, firstly, transports like IPC may not have a firm notion of a message origin. Secondly, transports that have some notion may not have a reliable one — a TCP disconnect may mean a new sender, or it may mean a temporary loss in network connectivity.

For this reason, sender information must be included by the application if required. Allocating 6 randomly-generated bytes in the message for the lifetime of the connection is sufficient for most purposes. For longer-lived applications, an UUID is more suitable.

### Socket Types

NN_REQ

  Used to implement the client application that sends requests and receives replies.

NN_REP

  Used to implement the stateless worker that receives requests and sends replies.

### Socket Options

NN_REQ_RESEND_IVL

  This option is defined on the full REQ socket. If reply is not received in specified amount of milliseconds, the request will be automatically resent. The type of this option is int. Default value is 60000 (1 minute).

## SEE ALSO

nn_bus(7) nn_pubsub(7) nn_pipeline(7) nn_survey(7) nn_pair(7) nanomsg(7)

## AUTHORS

Martin Sustrik