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Article contents:== Outdated egg! This is an egg for CHICKEN 4, the unsupported old release. You're almost certainly looking for [[/eggref/5/zmq|the CHICKEN 5 version of this egg]], if it exists. If it does not exist, there may be equivalent functionality provided by another egg; have a look at the [[https://wiki.call-cc.org/chicken-projects/egg-index-5.html|egg index]]. Otherwise, please consider porting this egg to the current version of CHICKEN. [[tags: egg]] == zmq [[toc:]] === WARNING This egg is currently unmaintained and has some known problems. Also, it doesn't support more recent libzmq releases. You may want to look at the [[nanomsg]] egg instead. === Description Bindings for the [[http://www.zeromq.org/|ZeroMQ (aka ZMQ, ØMQ or 0MQ)]] [[http://api.zeromq.org/|API]]. To get an idea of what ZeroMQ is and how it can be used, read the [[http://zguide.zeromq.org/|ZeroMQ Guide]]. The binding is currently fairly low-level as it mostly directly maps to the C API with only a few abstractions to make it more Scheme-like. More of those will follow in future versions. === Author [[/users/moritz-heidkamp|Moritz Heidkamp]] === Requirements You only need to have the [[/egg/foreigners|foreigners egg]] as well as [[http://www.zeromq.org/area:download|libzmq]] including its header files installed. Note that at least version 2.2 of ZeroMQ is required, which is a stable release from 2012-04-04. Version 3.x and up are not supported. === Documentation Currently, the {{zmq}} egg provides bindings for interacting with ZeroMQ contexts, sockets, messages and poll-items. ==== General <procedure>(zmq-version)</procedure> Returns the ZeroMQ version as a list of the form {{(major minor patch)}}. ==== Contexts <parameter>(zmq-default-context [context])</parameter> The ZeroMQ {{context}} used by all {{make-socket}} calls as the default context argument. Usually, you only need one context per application (unless you know what you need more than one for). Note that this parameter is initialized lazily upon the first call to {{make-socket}}. See also: {{zmq-io-threads}}. <parameter>(zmq-io-threads [number])</parameter> {{number}} of I/O threads to use for the {{zmq-default-context}}. Default: {{1}}. <procedure>(make-context number)</procedure> Creates a new ZeroMQ context using {{number}} I/O threads. <procedure>(context? context)</procedure> Check whether {{context}} is a ZeroMQ context. ==== Sockets <procedure>(make-socket type [context])</procedure> Create a ZeroMQ socket of {{type}}, which must be one of the symbols {{pull}}, {{push}}, {{pair}}, {{pub}}, {{sub}}, {{req}}, {{rep}}, {{xreq}} or {{xrep}}. See the [[http://api.zeromq.org/zmq_socket.html|zmq_socket documentation]] for information about what the different types mean. {{context}} must be a ZeroMQ context and is {{zmq-default-context}} by default. <procedure>(socket? socket)</procedure> Check whether {{socket}} is a ZeroMQ socket. <procedure>(close-socket socket)</procedure> Close the ZeroMQ {{socket}}. This is usually done by the finalizer so you only have to call this if you want to close a socket early for whatever reason. <procedure>(bind-socket socket endpoint)</procedure> Bind {{socket}} to {{endpoint}} which must be given as a string of the format {{transport://address}} (for details, see the documentation for [[http://api.zeromq.org/zmq_bind.html|zmq_bind]]). <procedure>(connect-socket socket endpoint)</procedure> Connect {{socket}} to {{endpoint}} which is given as a string of the format {{transport://address}} (for details, see the documentation for [[http://api.zeromq.org/zmq_connect.html|zmq_connect]]). <procedure>(socket-option-set! socket option value)</procedure> Destructively set {{option}} (a symbol) of {{socket}} to {{value}} (type depending on the respective {{option}}). The following options are available: ; hwm : high water mark (integer, maximum number of outstanding messages) ; swap : disk offload size (integer, bytes) ; affinity : I/O thread affinity (integer, bitmap) ; identity : socket identity (string, max. 255 bytes) ; subscribe : add message filter (string, message prefix) ; unsubscribe : remove message filter (string, message prefix) ; rate : multicast data rate (integer, kilobits per second) ; recovery-ivl : multicast recovery interval (integer, seconds) ; mcast-loop : multicast loopback (boolean) ; sndbuf : kernel transmit buffer size (integer, bytes, 0 for OS default) ; rcvbuf : kernel receive buffer size (integer, bytes, 0 for OS default) For more detailed descriptions of the options, see the [[http://api.zeromq.org/zmq_setsockopt.html|documentation for zmq_setsockopt]]. <procedure>(socket-option socket option)</procedure> Retrieve {{socket}}'s current {{option}} value. {{option}} must be given as one the symbols {{hwm}}, {{swap}}, {{affinity}}, {{rate}}, {{recovery-ivl}}, {{sndbuf}}, {{rcvbuf}}, {{rcvmore}}, {{mcast-loop}} or {{identity}}. For descriptions of the individual options see the [[http://api.zeromq.org/zmq_getsockopt.html|documentation for zmq_getsockopt]]. <procedure>(socket-fd socket)</procedure> Retrieve the {{socket}}'s file descriptor which can be used for traditional polling purposes. It is especially useful in conjunction with Chicken's SRFI-18 extension {{thread-wait-for-i/o!}} to be able to idly wait for messages in a separate thread. Note that the file descriptor is edge-triggered. ==== Communication <procedure>(send-message socket message #!key non-blocking send-more)</procedure> Send {{message}} via {{socket}} with {{message}} being a string or a blob. If {{non-blocking}} is {{#t}}, the function call will not block (default: {{#f}}). If {{send-more}} is {{#t}}, mark this message as part of a multi-part messaging and that further parts are to follow (see [[http://api.zeromq.org/zmq_send.html#_multi_part_messages|the documentation about multi-part messages for more information]], default: {{#f}}). <procedure>(receive-message socket #!key non-blocking as)</procedure> Receive the next message from {{socket}}. By default, the message data is returned as a string. This can be changed using the {{as}} argument. It can either be {{string}}, {{blob}} or a procedure. The latter will be called with a data pointer and an integer (the number of bytes). The value returned by the procedure will be the return value of {{receive-message}} and should make sure to read the message data. If {{non-blocking}} is {{#t}}, the function call will not block and return {{#f}} if no message is available (default: {{#f}}). <procedure>(receive-message* socket #!key as)</procedure> Receive the next message from {{socket}}. The {{as}} argument works the same way as {{receive-message}}'s does. This procedure will read blockingly but only block the current thread instead of the whole process. Also, it will allow signals to be handled immediately and is thus the recomended way for reading messages blockingly even for single-threaded programs. This procedure has been added in version 0.1.1. ==== Polling <procedure>(make-poll-item socket/fd #!key in out)</procedure> Create a ZeroMQ {{poll-item}} for {{socket/fd}} which can either be a ZeroMQ socket or a POSIX file descriptor. The keyword arguments {{in}} and {{out}} are booleans indicating whether the item should poll for incoming or outgoing data. Both are {{#f}} by default so make sure to pass at least one as {{#t}}. <procedure>(poll-item-fd item)</procedure> Return {{item}}'s POSIX file descriptor if is has been created with one (see {{make-poll-item}}). <procedure>(poll-item-socket item)</procedure> Return {{item}}'s socket if is has been created with one (see {{make-poll-item}}). <procedure>(poll-item-in? item)</procedure> Check whether {{item}}'s socket or file descriptor is ready for reading. <procedure>(poll-item-out? item)</procedure> Check whether {{item}}'s socket or file descriptor is ready for writing. <procedure>(poll-item-error? item)</procedure> Check whether there is an error condition present on {{item}}'s file descriptor. This will never be the case for ZeroMQ sockets. <procedure>(poll poll-items timeout/block)</procedure> Poll the poll-item list {{poll-items}} for activity. {{timeout/block}} can either be {{#t}} which will block until one of the {{poll-items}} is ready. When {{#f}} is passed the call will not block and return {{#f}} when no {{poll-item}} is ready. Alternatively, an integer may be passed, indicating the number of microseconds to wait for activity. The return value is a number indicating how many {{poll-items}} are ready. === Changelog ; 0.1.0 : deprecate message-* procedures and message record type. ; 0.1.1 : add receive-message* for better blocking reads === License Copyright (C) 2010-2012 Moritz Heidkamp This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA Description of your changes:

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