= 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 Scalability 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 possible values for _OPTION_ are described below.

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`.

When using the long form of an option (names prefixed with with `--`), if the
option takes a value then the value may be supplied by appending the option
with an equals sign and the value (e.g. `--subscribe=times`), by appending
the option with a colon and the value (e.g. `--subscribe:tribune`) or by
providing the data as the next program argument (e.g. `--subscribe herald`).

When using short form options (a single letter prefixed with a `-`),
if the option takes a value it may either be immediately appended to
the value (e.g. `-L5678`) or provided as the next program argument
(e.g. `-L 5678`).

POSIX style option clustering of single letter options is not supported;
each option must be presented as a separate argument to the program.

=== Generic Options
*-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. (((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 xref:nng_pair.7.adoc[_pair_] protocol instead of version 1.

*--subscribe*=_TOPIC_::
  Subscribe to _TOPIC_.  This option can only be used with the
  xref:nng_sub.7.adoc[_sub_] 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.

*--count=*=_COUNT_::
  Limit the number of iterations when looping to _COUNT_ iterations.
  For protocols that only send, this will only send _COUNT_ messages before
  exiting.
  For protocols that only receive, this will only receive _COUNT_ messages
  before exiting.
  For protocols that involve a full exchange, this will only perform _COUNT_
  exchanges (each exchange is characterized by at most a single send, and
  one or more receives.)
  If _COUNT_ is zero, then an infinite number of iterations is performed.

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

*--bus, --bus0*::
  Select the xref:nng_bus.7.adoc[_bus_] version 0 protocol.
  This protocol can send and receive messages to and from other _bus_ version 0
  peers.

*--req, --req0*::
  Select the xref:nng_req.7.adoc[_req_] version 0 protocol.
  This protocol sends messages to xref:nng_rep.7.adoc[_rep_] version 0
  peers and receives replies from them.

*--rep, --rep0*::
  Select the xref:nng_rep.7.adoc[_rep_] version 0 protocol.
  This protocol receives messages from xref:nng_req.7.adoc[_req_] version 0 peers
  and can send replies to them.

*--pub, --pub0*::
  Select the xref:nng_pub.7.adoc[_pub_] version 0 protocol.
  This protocol sends messages to xref:nng_sub.7.adoc[_sub_] version peers.

*--sub, --sub0*::
  Select the xref:nng_sub.7.adoc[_sub_] version 0 protocol.
  This protocol receives messages from xref:nng_pub.7.adoc[_pub_] version
  0 peers, and filters them based on subscriptions set with *--subscribe*.

*--push, --push0*::
  Select the xref:nng_push.7.adoc[_push_] version 0 protocol.
  This protocol sends messages to xref:nng_pull.7.adoc[_pull_] version 0 peers.
  A given message is normally only delivered to a single peer.

*--pull, --pull0*::
  Select the xref:nng_pull.7.adoc[_pull_] version 0 protocol.
  This protocol receives
  messages from xref:nng_push.7.adoc[_push_] version 0 peers.

*--pair0*::
  Select the xref:nng_pair.7.adoc[_pair_] version 0 protocol.
  This protocol can send and receive messages with one connected _pair_
  version 0 peer.

*--pair1*::
  Select the xref:nng_pair.7.adoc[_pair_] version 1 protocol.
  This protocol can send and receive messages with one connected _pair_
  version 1 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 xref:nng_surveyor.7.adoc[_surveyor_] version 0 protocol.
  This protocol sends a survey request to xref:nng_respondent.7.adoc[_respondent_]
  version 0 peers, and then receives replies from them.

*--respondent, --respondent0*::
  Select the xref:nng_respondent.7.adoc[_respondent_] version 0 protocol.
  This protocol receives survey requests from xref:nng_surveyor.7.adoc[_surveyor_]
  version 0 peers, and can send a reply to them.

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

TIP: While legacy _nanocat_ only supported one peer, _nngcat_ 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.

*-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.

*--recv-maxsz*=_COUNT_::
  Set the maximum message size socket will accept to _COUNT_ bytes.
  Messages larger than this will be discarded.
  The default is 1048576 (1 MB).
  To eliminate any restriction, use 0.

*--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`::: (((hex))) Messages are printed as quoted strings, with every byte appearing as an escaped hexadecimal value, such as `\x2E`.

`msgpack`::: (((msgpack)))(((MessagePack)))
Messages are emitted as https://msgpack.org[MessagePack] "bin format"
(byte arrays).

=== 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. If _FILE_ is _-_ the message body will be read from standard input.

*-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 conjunction 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

[.text-left]
xref:libnng.3.adoc[libnng(3)],
xref:nng.7.adoc[nng(7)],
xref:nng_bus.7.adoc[nng_bus(7)],
xref:nng_pair.7.adoc[nng_pair(7)],
xref:nng_pub.7.adoc[nng_pub(7)],
xref:nng_pull.7.adoc[nng_pull(7)],
xref:nng_push.7.adoc[nng_push(7)],
xref:nng_sub.7.adoc[nng_sub(7)],
xref:nng_rep.7.adoc[nng_rep(7)],
xref:nng_req.7.adoc[nng_req(7)],
xref:nng_respondent.7.adoc[nng_respondent(7)],
xref:nng_surveyor.7.adoc[nng_surveyor(7)]
