= nngcat(1)
//
// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
// Copyright 2018 Capitar IT Group BV <info@capitar.com>
//
// This document is supplied under the terms of the MIT License, a
// copy of which should be located in the distribution where this
// file was obtained (LICENSE.txt).  A copy of the license may also be
// found online at https://opensource.org/licenses/MIT.
//

== NAME

nngcat - command line access to Scalabity Protocols

== SYNOPSIS

*nngcat* --help

*nngcat* --version

*nngcat* [_OPTION_]... 

== DESCRIPTION

The _nngcat_ utility provides command line access to the Scalability
Protocols, making it possible to write shell scripts that interact
with other peers in a Scalability Protocols topology, by both sending and
receiving messages.

== OPTIONS

The following options may be supplied for _OPTION_.

TIP: The _nngcat_ utility accepts shortened versions of these options, as long
as the supplied option is unambiguous.  For example `--comp` can be used in lieu
of `--compat`, but `--re` may not be used for anything because it could mean
any of `--req`, `--rep`, or `--respondent`.

Options that take values may be separated from their value either by an
equa

=== Generic
*-h, --help*::
  Get usage help.
*-V, --version*::
  Print the version and exit.
*-v, --verbose*::
  Select verbose operation.
*-q, --silent*::
  Select silent operation.
*--compat*::
  Compatible mode.  This cause _nngcat_ to behave more like the legacy
  _nanocat_ application.  In this mode connections are made asynchronously,
  and the *--pair* option selects version 0 of the <<nng_pair#,PAIR>> protocol
  instead of version 1.
*--subscribe*=_TOPIC_::
  Subscribe to _TOPIC_.  This option can only be used with the
  <<nng_sub#,SUBv0>> protocol.  The _TOPIC_ is checked against the first bytes
  of messages received, and messages are discarded if they do not match.
  This may be specified multiple times to subscribe to multiple topics.  If
  not specified at all, then a default subscription to everything is assumed.

=== Protocol Selection
NOTE: At least one protocol must be selected.

*--bus, --bus0*::
  Select the <<nng_bus#,BUSv0>> protocol.  This protocol can send
  and receive messages to and from other <<nng_bus#,BUSv0>> peers.

*--req, --req0*::
  Select the <<nng_req#,REQv0>> protocol.  This protocol sends
  messages to <<nng_rep#,REPv0>> peers and receives replies from them.

*--rep, --rep0*::
  Select the <<nng_rep#,REPv0>> protocol.  This protocol receives
  messages from <<nng_req#,REQv0>> peers and can send replies to them.

*--pub, --pub0*::
  Select the <<nng_pub#,PUBv0>> protocol.  This protocol sends
  messages to <<nng_sub#,SUBv0>> peers.

*--sub, --sub0*::
  Select the <<nng_sub#,SUBv0>> protocol.  This protocol receives
  messages from <<nng_pub#,PUBv0>> peers, and filters them based on
  subscriptions set with *--subscribe*.
  
*--push, --push0*::
  Select the <<nng_push#,PUSHv0>> protocol.  This protocol sends
  messages to <<nng_pull#,PULLv0>> peers. A given message is normally
  only delivered to a single peer.

*--pull, --pull0*::
  Select the <<nng_pull#,PULLv0>> protocol.  This protocol receives
  messages from <<nng_push#,PUSHv0>> peers.

*--pair0*::
  Select the <<nng_pair#,PAIRv0>> protocol.  This protocol can send and
  receive messages with one connected <<nng_pair#,PAIRv0>> peer.

*--pair1*::
  Select the <<nng_pair#,PAIRv1>> protocol.  This protocol can send and
  receive messages with one connected <<nng_pair#,PAIRv1>> peer. It 
  is not supported in *--compat* mode.  (Polyamorous mode is not supported 
  in _nngcat_, although peers may be using polyamorous mode.)

*--pair*::
  Acts as an alias for *--pair1*, unless *--compat* mode is selected, in
  which case it acts as an alias for *--pair0*.

*--surveyor, --surveyor0*::
  Select the <<nng_surveyor#,SURVEYORv0>> protocol.  This protocol sends
  a survey request to <<nng_respondent#,RESPONDENTv0>> peers, and then
  receives replies from them.

*--respondent, --respondent0*::
  Select the <<nng_respondent#,RESPONDENTv0>> protocol.  This protocol receives
  survey requests from <<nng_survey#,SURVEYORv0>> peers, and can send a reply
  to them.

=== Peer Selection
NOTE: At least one peer address must be selected.

TIP: While legacy _nanocat_ only supported one peer, _nng_ can support
more than one peer on a given connection.

*--connect, --dial*=_URL_::
  Connect to the peer at the address specified by _URL_.

*--bind, --listen*=_URL_::
  Bind to, and accept connections from peers, at the address specified by _URL_.

*-x, --connect-ipc*=_PATH_::
  Connect to the IPC path specified by _PATH_.  This is the same as 
  *--connect*=ipc://_PATH_.

*-X, --bind-ipc*=_PATH_::
  Bind to the IPC path specified by _PATH_.  This is the same as 
  *--bind*=ipc://_PATH_.

*-l, --connect-local*=_PORT_::
  Connect to `localhost` at the TCP port specified by _PORT_.  This is the same
  as *--connect*=tcp://127.0.0.1:__PORT__.

*-L, --bind-local*=_PORT_::
  Bind to the TCP port specified by _PORT_.  This is the same as 
  *--bind*=tcp://127.0.0.1:__PORT__.

=== Receive Options

Data messages received can be formatted in different ways.  These
options can only be specified when using a protocol that receives messages.

*--format*=_FORMAT_::
  Format data as indicated.  The _FORMAT_ can be any of: +
  `no`:::
    No output at all.
  `raw`:::
    Raw output, every byte received is sent to standard output.
  `ascii`:::
    ASCII safe, printable ASCII is emitted verbatim, with other bytes
    substituted with `.` (period).
  `quoted`:::
    Messages are printed as quoted strings, using C language conventions.
  `hex`:::
    Messages are printed as quoted strings, with every byte appearing as
    an escaped hexadecimal value, such as `\x2E`.
  `msgpack`:::
    Messages are emitted as https://msgpack.org[MessagePack] "bin format"
    (byte arrays).

*-A, --ascii*::
  The same as specifying *--format*=`ascii`.

*-Q, --quoted*::
  The same as specifying *--format*=`quoted`.

*--hex*::
  The same as specifying *--format*=`hex`.

*--msgpack*::
  The same as specifying *--format*=`msgpack`.

*--raw*::
  The same as specifying *--format*=`raw`.

*--receive-timeout*=_SEC_::
  Give up receiving messages after _SEC_ seconds pass without any received
  messages.

=== Transmit Options

Protocols that support sending data can use these options to select
the data. 

*-D, --data*=_DATA_::
  Use _DATA_ for the body of outgoing messages.

*-F, --file*=_FILE_::
  Use _FILE_ for the body of outgoing messages.

*-i, --interval*=_SEC_::
  For protocols that send unsolicited data (as opposed to those that
  send data only in response to received messages), this will resend the
  outgoing message at repeating intervals of _SEC_ seconds.

*-d, --delay*=_SEC_::
  Wait _SEC_ seconds before sending the first outgoing message.  This is
  useful to let connections establish before sending data, thereby avoiding
  message loss.

*--send-timeout*=_SEC_::
  Give up trying to send a message after _SEC_ seconds.

=== TLS Options

These options are only present if TLS is configured; they are ignored
when using addresses that are not secured with TLS.

*-k, --insecure*::
  Skip peer validation.

*-E, --cert*=_FILE_::
  Load own certificate from _FILE_.

*--key*=_FILE_::
  Load own key from _FILE_.  Should be used in conjuction with *--cert*.  If 
  not specified, and *--cert* is specified, then a single file containing both 
  the private key and the associated certificate is assumed.

*--cacert*=_FILE_::
  Load CA certificates from _FILE_.  These CAs ("Certificate Authorities") are
  used as trust roots when validating certificates presented by peers.

=== ZeroTier Options

These options are only present if ZeroTier is configured; they are ignored
otherwise.

*--zt-home*=_DIRECTORY_::
  Directory for persistent ZeroTier node (key material, etc.)  This directory
  must already exist.  Only one program may use a ZeroTier node at a time;
  file locking is used to prevent this.

== EXAMPLES

.Echo service using request/reply.
[source,sh]
----
$ addr="tcp://127.0.0.1:4567"
$ nngcat --rep --listen=${addr} --data="42" --quoted &
$ nngcat --req --dial=${addr} --data="what is the answer?" --quoted
"what is the answer?"
"42"
----

.Send a chime every hour (3600 seconds).
[source,sh]
----
$ addr=ipc:///grandpa_clock
$ nngcat --pub --listen=${addr} --data "cuckoo" --interval 3600 &
$ nngcat --sub --dial=${addr} --quoted &
"cuckoo"
----

== SEE ALSO

<<libnng#,libnng(3)>>,
<<nng#,nng(3)>>,
<<nng_bus#,nng_bus(7)>>,
<<nng_pair#,nng_pair(7)>>,
<<nng_pub#,nng_pub(7)>>,
<<nng_pull#,nng_pull(7)>>,
<<nng_push#,nng_push(7)>>,
<<nng_sub#,nng_sub(7)>>,
<<nng_rep#,nng_rep(7)>>,
<<nng_req#,nng_req(7)>>,
<<nng_respondent#,nng_respondent(7)>>,
<<nng_surveyor#,nng_surveyor(7)>>

