zmqc

netcat for ØMQ.

View the Project on GitHub zacharyvoase/zmqc

zmqc is a small but powerful command-line interface to ØMQ. It allows you to create a socket of a given type, bind or connect it to multiple addresses, set options on it, and receive or send messages over it using standard I/O, in the shell or in scripts. It's useful for debugging and experimenting with most possible network topologies.

Usage

zmqc [-h] [-v] [-0] [-r | -w] (-b | -c) SOCK_TYPE \
     [-o SOCK_OPT=VALUE...] address [address ...]

Mode

Whether to read from or write to the socket. For PUB/SUB sockets, this option is invalid since the behavior will always be write and read respectively. For REQ/REP sockets, zmqc will alternate between reading and writing as part of the request/response cycle.

-r, --read

Read messages from the socket onto stdout.

-w, --write

Write messages from stdin to the socket.

Behavior

-b, --bind

Bind to the specified address(es).

-c, --connect

Connect to the specified address(es).

Socket Parameters

SOCK_TYPE

Which type of socket to create. Must be one of PUSH, PULL, PUB, SUB, REQ, REP or PAIR. See man zmq_socket for an explanation of the different types. DEALER and ROUTER sockets are currently unsupported.

-o SOCK_OPT=VALUE, --option SOCK_OPT=VALUE

Socket option names and values to set on the created socket. Consult man zmq_setsockopt for a comprehensive list of options. Note that you can safely omit the ZMQ_ prefix from the option name. If the created socket is of type SUB, and no SUBSCRIBE options are given, the socket will automatically be subscribed to everything.

address

One or more addresses to bind/connect to. Must be in full ZMQ format (e.g. tcp://<host>:<port>)

Examples

zmqc -rc SUB 'tcp://127.0.0.1:5000'

Subscribe to tcp://127.0.0.1:5000, reading messages from it and printing them to the console. This will subscribe to all messages by default (you don't need to set an empty SUBSCRIBE option). Alternatively:

zmqc -rc SUB -o SUBSCRIBE='com.organization.' 'tcp://127.0.0.1:5000'

This will subscribe to all messages starting with com.organization..


ls | zmqc -wb PUSH 'tcp://*:4000'

Send the name of every file in the current directory as a message from a PUSH socket bound to port 4000 on all interfaces. Don't forget to quote the address to avoid glob expansion.


zmqc -rc PULL 'tcp://127.0.0.1:5202' | \
    tee $TTY | \
    zmqc -wc PUSH 'tcp://127.0.0.1:5404'

Read messages coming from a PUSH socket bound to port 5202 (note that we're connecting with a PULL socket), echo them to the active console, and forward them to a PULL socket bound to port 5404 (so we're connecting with a PUSH).


zmqc -n 10 -0rb PULL 'tcp://*:4123' | \
    xargs -0 grep 'pattern'

Bind to a PULL socket on port 4123, receive 10 messages from the socket (with each message representing a filename), and grep the files for 'pattern'. The -0 option means messages will be NULL-delimited rather than separated by newlines, so that filenames with spaces in them are not considered two separate arguments by xargs.


echo "hello" | zmqc -c REQ 'tcp://127.0.0.1:4000'

Send the string hello through a REQ socket connected to localhost on port 4000, print whatever you get back, and finish. In this way, REQ sockets can be used for a rudimentary form of RPC in shell scripts.


coproc zmqc -b REP 'tcp://*:4000'
tr -u '[a-z]' '[A-Z]' <&p >&p &
echo "hello" | zmqc -c REQ 'tcp://127.0.0.1:4000'

First, start a REP socket listening on port 4000. The coproc shell command runs this as a shell coprocess, which allows us to run the next line. tr will read its input from the REP socket's output, translate all lowercase characters to uppercase, and send them back to the REP socket's input (the -u option enables unbuffered streaming). This, again, is run in the background. Finally, connect a REQ socket to that REP socket and send the string hello through it: you should just see the string HELLO printed on stdout.

Installation

pip install zmqc

zmqc is released under the Unlicense.