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.

Installation

pip install zmqc

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. This 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. 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.

(Un)license

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.

In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to http://unlicense.org/