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. 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 pair protocol
           instead of version 1.

       --subscribe=TOPIC
           Subscribe to TOPIC. This option can only be used with the 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 bus version 0 protocol. This protocol can send and receive messages to and from other bus
           version 0 peers.

       --req, --req0
           Select the req version 0 protocol. This protocol sends messages to rep version 0 peers and receives
           replies from them.

       --rep, --rep0
           Select the rep version 0 protocol. This protocol receives messages from req version 0 peers and can
           send replies to them.

       --pub, --pub0
           Select the pub version 0 protocol. This protocol sends messages to sub version peers.

       --sub, --sub0
           Select the sub version 0 protocol. This protocol receives messages from pub version 0 peers, and
           filters them based on subscriptions set with --subscribe.

       --push, --push0
           Select the push version 0 protocol. This protocol sends messages to pull version 0 peers. A given
           message is normally only delivered to a single peer.

       --pull, --pull0
           Select the pull version 0 protocol. This protocol receives messages from push version 0 peers.

       --pair0
           Select the pair version 0 protocol. This protocol can send and receive messages with one connected
           pair version 0 peer.

       --pair1
           Select the 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 surveyor version 0 protocol. This protocol sends a survey request to respondent version 0
           peers, and then receives replies from them.

       --respondent, --respondent0
           Select the respondent version 0 protocol. This protocol receives survey requests from 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
                Messages are printed as quoted strings, with every byte appearing as an escaped hexadecimal
               value, such as \x2E.

           msgpack

               Messages are emitted as MessagePack <https://msgpack.org> "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.

           $ 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).

           $ addr=ipc:///grandpa_clock
           $ nngcat --pub --listen=${addr} --data "cuckoo" --interval 3600 &
           $ nngcat --sub --dial=${addr} --quoted &
           "cuckoo"

SEE ALSO

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

                                                   2025-04-20                                          NNGCAT(1)