Chicken Scheme bindings for the lightweight ZMQ-alternative nanomsg
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readme.md

chicken-nanomsg

Chicken Scheme bindings for the lightweight ZMQ-alternative, nanomsg. There exists Chicken ZMQ bindings, but this turned out to be a little troublesome with zmq_poll blocking other srfi-18 threads.

Why nanomsg

Nanomsg is smaller, written in C, has a simplified API (sockets are simple ints), no multipart messages, and has explicit support for poll on a socket's recv file-descriptor, which integrates well with Chicken Scheme.

Requirements

This egg requires nanomsg-1.0.0 or higher.

API

[procedure] (nn-socket protocol [domain])

Create a nanomsg socket. Protocol can be any of the symbols pair, pub, sub, pull, push, req, rep, surveyor, respondent or bus. Domain can be the symbol sp or sp-raw, and defaults to sp. The returned socket is automatically closed with nn-close when it is garbage-collected.

[procedure] (nn-socket* protocol [domain])

Just like nn-socket, but does not attach a finalizer on the returned socket object. You must manually call nn-close on the socket after use.

[procedure] (nn-bind socket address)

Binds nanomsg socket to address, where address is a string of the form "ipc:///var/ipc/music.nn.pair" or "tcp://0.0.0.0:10080". If the nn-library can't parse the address string, it throws an "Illegal argument" error.

[procedure] (nn-connect socket address)

Connects nanomsg socket socket to address.

[procedure] (nn-subscribe socket prefix)

Set the NN_SUB_SUBSCRIBE option on socket which will make the socket receive to all messages that start with prefix.

Note that if this is never called, (nn-sock 'sub) sockets will never receive anything.

[procedure] (nn-send socket msg)

Send a message on socket, using the socket's semantics. msg must be a string. This will not block other srfi-18 threads. Returns the number of bytes sent.

[procedure] (nn-send* socket msg flags)

Like nn-send, but may block other srfi-18 threads when flags is 0. flags may be nn/dontwait in which case nn-send* always returns immediately, and returns #f is the operation would block (number of bytes otherwise).

[procedure] (nn-recv socket)

Receive a message from socket. This blocks until a message is received from nanomsg, but it does not block other srfi-18 threads. It always returns a string. An error is thrown if the socket is in an illegal state.

Note that memory is copied from the nanomsg buffer into a new scheme string.

[procedure] (nn-recv* socket flags)

Receive a message from socket. This will block other srfi-18 threads, unless the nn/dontwait flag is specified, in which case nn-recv* will exit immediately with either a message as a string or #f (for EAGAIN). An error is thrown if socket is in an illegal state.

Note that this can be combined with (nn-socket-rcvfd socket) for custom polling.

[procedure] (nn-close socket)

Explicitly close socket. This is normally not needed as this is done in the socket's finalizer.

[procedure] (nn-shutdown socket endpoint)

Removed endpoint from socket. See nn_shutdown.

[procedure] (nn-get-statistic socket statistic)

Retrieve a statistic from socket. statistic may be any one of these symbols: established-connections accepted-connections dropped-connections broken-connections connect-errors bind-errors accept-errors current-connections inprogress-connections current-ep-errors messages-sent messages-received bytes-sent bytes-received current-snd-priority. See nn_get_statistic.

[procedure] (nn-socket-name socket)
[procedure] (nn-socket-linger socket)
[procedure] (nn-socket-rcvtimeo socket)
[procedure] (nn-socket-sndtimeo socket)
[procedure] (nn-socket-rcvbuf socket)
[procedure] (nn-socket-sndbuf socket)
[procedure] (nn-socket-sndfd socket)
[procedure] (nn-socket-rcvfd socket)
[procedure] (nn-socket-protocol socket)
[procedure] (nn-socket-domain socket)
[procedure] (nn-socket-maxttl socket)
[procedure] (nn-socket-rcvmaxsize socket)
[procedure] (nn-socket-rcvprio socket)
[procedure] (nn-socket-sndprio socket)
[procedure] (nn-socket-reconnect-ivl-max socket)
[procedure] (nn-socket-reconnect-ivl socket)
[procedure] (nn-socket-ipv4only socket)
[procedure] (nn-req-socket-resend-ivl socket)

Retrieve the socket option associated with socket. Most of these also provide setters so that you can, for example, can do (set! (nn-socket-name s) "foo").

For other socket options, try nn-getsockopt/string, nn-getsockopt/int, nn-setsockopt/string and nn-setsockopt/int.

Development Status

These bindings to nanomsg 1.0.0 should be fairly complete, the only missing functionality is the control messages (nn_recvmsg, nn_sendmsg and nn_cmsg). Also, note that the egg hasn't undergode rigerous testing in the field yet.

Sample

;; test.scm
(import nanomsg)

(define s (nn-socket 'rep))
(nn-bind s "tcp://127.0.0.1:22022")

(let loop ((n 0))
  (nn-send s (conc (nn-recv s) " " n))
  (loop (add1 n)))

(nn-close s)

then test with the brilliant nanocat util that comes with nanomsg:

$ csi -s test.scm &
$ nanocat --req -l22022 -D"bottles of beer:" -A --interval 1