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diff --git a/doc/zmq_socket.txt b/doc/zmq_socket.txt deleted file mode 100644 index 2eab0fd..0000000 --- a/doc/zmq_socket.txt +++ /dev/null @@ -1,444 +0,0 @@ -zmq_socket(3) -============= - - -NAME ----- -zmq_socket - create 0MQ socket - - -SYNOPSIS --------- -*void *zmq_socket (void '*context', int 'type');* - - -DESCRIPTION ------------ -The 'zmq_socket()' function shall create a 0MQ socket within the specified -'context' and return an opaque handle to the newly created socket. The 'type' -argument specifies the socket type, which determines the semantics of -communication over the socket. - -The newly created socket is initially unbound, and not associated with any -endpoints. In order to establish a message flow a socket must first be -connected to at least one endpoint with linkzmq:zmq_connect[3], or at least one -endpoint must be created for accepting incoming connections with -linkzmq:zmq_bind[3]. - -.Key differences to conventional sockets -Generally speaking, conventional sockets present a _synchronous_ interface to -either connection-oriented reliable byte streams (SOCK_STREAM), or -connection-less unreliable datagrams (SOCK_DGRAM). In comparison, 0MQ sockets -present an abstraction of an asynchronous _message queue_, with the exact -queueing semantics depending on the socket type in use. Where conventional -sockets transfer streams of bytes or discrete datagrams, 0MQ sockets transfer -discrete _messages_. - -0MQ sockets being _asynchronous_ means that the timings of the physical -connection setup and tear down, reconnect and effective delivery are transparent -to the user and organized by 0MQ itself. Further, messages may be _queued_ in -the event that a peer is unavailable to receive them. - -Conventional sockets allow only strict one-to-one (two peers), many-to-one -(many clients, one server), or in some cases one-to-many (multicast) -relationships. With the exception of 'ZMQ_PAIR', 0MQ sockets may be connected -*to multiple endpoints* using _zmq_connect()_, while simultaneously accepting -incoming connections *from multiple endpoints* bound to the socket using -_zmq_bind()_, thus allowing many-to-many relationships. - -.Thread safety -0MQ 'sockets' are _not_ thread safe. Applications MUST NOT use a socket -from multiple threads except after migrating a socket from one thread to -another with a "full fence" memory barrier. - -.Socket types -The following sections present the socket types defined by 0MQ, grouped by the -general _messaging pattern_ which is built from related socket types. - - -Request-reply pattern -~~~~~~~~~~~~~~~~~~~~~ -The request-reply pattern is used for sending requests from a ZMQ_REQ _client_ -to one or more ZMQ_REP _services_, and receiving subsequent replies to each -request sent. - -The request-reply pattern is formally defined by http://rfc.zeromq.org/spec:28. - -ZMQ_REQ -^^^^^^^ -A socket of type 'ZMQ_REQ' is used by a _client_ to send requests to and -receive replies from a _service_. This socket type allows only an alternating -sequence of _zmq_send(request)_ and subsequent _zmq_recv(reply)_ calls. Each -request sent is round-robined among all _services_, and each reply received is -matched with the last issued request. - -If no services are available, then any send operation on the socket shall -block until at least one _service_ becomes available. The REQ socket shall -not discard messages. - -[horizontal] -.Summary of ZMQ_REQ characteristics -Compatible peer sockets:: 'ZMQ_REP', 'ZMQ_ROUTER' -Direction:: Bidirectional -Send/receive pattern:: Send, Receive, Send, Receive, ... -Outgoing routing strategy:: Round-robin -Incoming routing strategy:: Last peer -Action in mute state:: Block - - -ZMQ_REP -^^^^^^^ -A socket of type 'ZMQ_REP' is used by a _service_ to receive requests from and -send replies to a _client_. This socket type allows only an alternating -sequence of _zmq_recv(request)_ and subsequent _zmq_send(reply)_ calls. Each -request received is fair-queued from among all _clients_, and each reply sent -is routed to the _client_ that issued the last request. If the original -requester does not exist any more the reply is silently discarded. - -[horizontal] -.Summary of ZMQ_REP characteristics -Compatible peer sockets:: 'ZMQ_REQ', 'ZMQ_DEALER' -Direction:: Bidirectional -Send/receive pattern:: Receive, Send, Receive, Send, ... -Incoming routing strategy:: Fair-queued -Outgoing routing strategy:: Last peer - - -ZMQ_DEALER -^^^^^^^^^^ -A socket of type 'ZMQ_DEALER' is an advanced pattern used for extending -request/reply sockets. Each message sent is round-robined among all connected -peers, and each message received is fair-queued from all connected peers. - -When a 'ZMQ_DEALER' socket enters the 'mute' state due to having reached the -high water mark for all peers, or if there are no peers at all, then any -linkzmq:zmq_send[3] operations on the socket shall block until the mute -state ends or at least one peer becomes available for sending; messages are not -discarded. - -When a 'ZMQ_DEALER' socket is connected to a 'ZMQ_REP' socket each message sent -must consist of an empty message part, the _delimiter_, followed by one or more -_body parts_. - -[horizontal] -.Summary of ZMQ_DEALER characteristics -Compatible peer sockets:: 'ZMQ_ROUTER', 'ZMQ_REP', 'ZMQ_DEALER' -Direction:: Bidirectional -Send/receive pattern:: Unrestricted -Outgoing routing strategy:: Round-robin -Incoming routing strategy:: Fair-queued -Action in mute state:: Block - - -ZMQ_ROUTER -^^^^^^^^^^ -A socket of type 'ZMQ_ROUTER' is an advanced socket type used for extending -request/reply sockets. When receiving messages a 'ZMQ_ROUTER' socket shall -prepend a message part containing the _identity_ of the originating peer to the -message before passing it to the application. Messages received are fair-queued -from among all connected peers. When sending messages a 'ZMQ_ROUTER' socket shall -remove the first part of the message and use it to determine the _identity_ of -the peer the message shall be routed to. If the peer does not exist anymore -the message shall be silently discarded by default, unless 'ZMQ_ROUTER_MANDATORY' -socket option is set to '1'. - -When a 'ZMQ_ROUTER' socket enters the 'mute' state due to having reached the -high water mark for all peers, then any messages sent to the socket shall be dropped -until the mute state ends. Likewise, any messages routed to a peer for which -the individual high water mark has been reached shall also be dropped. - -When a 'ZMQ_REQ' socket is connected to a 'ZMQ_ROUTER' socket, in addition to the -_identity_ of the originating peer each message received shall contain an empty -_delimiter_ message part. Hence, the entire structure of each received message -as seen by the application becomes: one or more _identity_ parts, _delimiter_ -part, one or more _body parts_. When sending replies to a 'ZMQ_REQ' socket the -application must include the _delimiter_ part. - -[horizontal] -.Summary of ZMQ_ROUTER characteristics -Compatible peer sockets:: 'ZMQ_DEALER', 'ZMQ_REQ', 'ZMQ_ROUTER' -Direction:: Bidirectional -Send/receive pattern:: Unrestricted -Outgoing routing strategy:: See text -Incoming routing strategy:: Fair-queued -Action in mute state:: Drop - - -Publish-subscribe pattern -~~~~~~~~~~~~~~~~~~~~~~~~~ -The publish-subscribe pattern is used for one-to-many distribution of data from -a single _publisher_ to multiple _subscribers_ in a fan out fashion. - -The publish-subscribe pattern is formally defined by http://rfc.zeromq.org/spec:29. - -ZMQ_PUB -^^^^^^^ -A socket of type 'ZMQ_PUB' is used by a _publisher_ to distribute data. -Messages sent are distributed in a fan out fashion to all connected peers. -The linkzmq:zmq_recv[3] function is not implemented for this socket type. - -When a 'ZMQ_PUB' socket enters the 'mute' state due to having reached the -high water mark for a _subscriber_, then any messages that would be sent to the -_subscriber_ in question shall instead be dropped until the mute state -ends. The _zmq_send()_ function shall never block for this socket type. - -[horizontal] -.Summary of ZMQ_PUB characteristics -Compatible peer sockets:: 'ZMQ_SUB', 'ZMQ_XSUB' -Direction:: Unidirectional -Send/receive pattern:: Send only -Incoming routing strategy:: N/A -Outgoing routing strategy:: Fan out -Action in mute state:: Drop - - -ZMQ_SUB -^^^^^^^ -A socket of type 'ZMQ_SUB' is used by a _subscriber_ to subscribe to data -distributed by a _publisher_. Initially a 'ZMQ_SUB' socket is not subscribed to -any messages, use the 'ZMQ_SUBSCRIBE' option of linkzmq:zmq_setsockopt[3] to -specify which messages to subscribe to. The _zmq_send()_ function is not -implemented for this socket type. - -[horizontal] -.Summary of ZMQ_SUB characteristics -Compatible peer sockets:: 'ZMQ_PUB', 'ZMQ_XPUB' -Direction:: Unidirectional -Send/receive pattern:: Receive only -Incoming routing strategy:: Fair-queued -Outgoing routing strategy:: N/A - - -ZMQ_XPUB -^^^^^^^^ -Same as ZMQ_PUB except that you can receive subscriptions from the peers -in form of incoming messages. Subscription message is a byte 1 (for -subscriptions) or byte 0 (for unsubscriptions) followed by the subscription -body. Messages without a sub/unsub prefix are also received, but have no -effect on subscription status. - -[horizontal] -.Summary of ZMQ_XPUB characteristics -Compatible peer sockets:: 'ZMQ_SUB', 'ZMQ_XSUB' -Direction:: Unidirectional -Send/receive pattern:: Send messages, receive subscriptions -Incoming routing strategy:: N/A -Outgoing routing strategy:: Fan out -Action in mute state:: Drop - - -ZMQ_XSUB -^^^^^^^^ -Same as ZMQ_SUB except that you subscribe by sending subscription messages to -the socket. Subscription message is a byte 1 (for subscriptions) or byte 0 -(for unsubscriptions) followed by the subscription body. Messages without a -sub/unsub prefix may also be sent, but have no effect on subscription status. - -[horizontal] -.Summary of ZMQ_XSUB characteristics -Compatible peer sockets:: 'ZMQ_PUB', 'ZMQ_XPUB' -Direction:: Unidirectional -Send/receive pattern:: Receive messages, send subscriptions -Incoming routing strategy:: Fair-queued -Outgoing routing strategy:: N/A -Action in mute state:: Drop - - -Pipeline pattern -~~~~~~~~~~~~~~~~ -The pipeline pattern is used for distributing data to _nodes_ arranged in -a pipeline. Data always flows down the pipeline, and each stage of the pipeline -is connected to at least one _node_. When a pipeline stage is connected to -multiple _nodes_ data is round-robined among all connected _nodes_. - -The pipeline pattern is formally defined by http://rfc.zeromq.org/spec:30. - -ZMQ_PUSH -^^^^^^^^ -A socket of type 'ZMQ_PUSH' is used by a pipeline _node_ to send messages -to downstream pipeline _nodes_. Messages are round-robined to all connected -downstream _nodes_. The _zmq_recv()_ function is not implemented for this -socket type. - -When a 'ZMQ_PUSH' socket enters the 'mute' state due to having reached the -high water mark for all downstream _nodes_, or if there are no downstream -_nodes_ at all, then any linkzmq:zmq_send[3] operations on the socket shall -block until the mute state ends or at least one downstream _node_ -becomes available for sending; messages are not discarded. - -[horizontal] -.Summary of ZMQ_PUSH characteristics -Compatible peer sockets:: 'ZMQ_PULL' -Direction:: Unidirectional -Send/receive pattern:: Send only -Incoming routing strategy:: N/A -Outgoing routing strategy:: Round-robin -Action in mute state:: Block - - -ZMQ_PULL -^^^^^^^^ -A socket of type 'ZMQ_PULL' is used by a pipeline _node_ to receive messages -from upstream pipeline _nodes_. Messages are fair-queued from among all -connected upstream _nodes_. The _zmq_send()_ function is not implemented for -this socket type. - -[horizontal] -.Summary of ZMQ_PULL characteristics -Compatible peer sockets:: 'ZMQ_PUSH' -Direction:: Unidirectional -Send/receive pattern:: Receive only -Incoming routing strategy:: Fair-queued -Outgoing routing strategy:: N/A -Action in mute state:: Block - - -Exclusive pair pattern -~~~~~~~~~~~~~~~~~~~~~~ -The exclusive pair pattern is used to connect a peer to precisely one other -peer. This pattern is used for inter-thread communication across the inproc -transport. - -The exclusive pair pattern is formally defined by http://rfc.zeromq.org/spec:31. - -ZMQ_PAIR -^^^^^^^^ -A socket of type 'ZMQ_PAIR' can only be connected to a single peer at any one -time. No message routing or filtering is performed on messages sent over a -'ZMQ_PAIR' socket. - -When a 'ZMQ_PAIR' socket enters the 'mute' state due to having reached the -high water mark for the connected peer, or if no peer is connected, then -any linkzmq:zmq_send[3] operations on the socket shall block until the peer -becomes available for sending; messages are not discarded. - -NOTE: 'ZMQ_PAIR' sockets are designed for inter-thread communication across -the linkzmq:zmq_inproc[7] transport and do not implement functionality such -as auto-reconnection. 'ZMQ_PAIR' sockets are considered experimental and may -have other missing or broken aspects. - -[horizontal] -.Summary of ZMQ_PAIR characteristics -Compatible peer sockets:: 'ZMQ_PAIR' -Direction:: Bidirectional -Send/receive pattern:: Unrestricted -Incoming routing strategy:: N/A -Outgoing routing strategy:: N/A -Action in mute state:: Block - - -Native Pattern -~~~~~~~~~~~~~~ -The native pattern is used for communicating with TCP peers and allows -asynchronous requests and replies in either direction. - - -ZMQ_STREAM -^^^^^^^^^^ -A socket of type 'ZMQ_STREAM' is used to send and receive TCP data from a -non-0MQ peer, when using the tcp:// transport. A 'ZMQ_STREAM' socket can -act as client and/or server, sending and/or receiving TCP data asynchronously. - -When receiving TCP data, a 'ZMQ_STREAM' socket shall prepend a message part -containing the _identity_ of the originating peer to the message before passing -it to the application. Messages received are fair-queued from among all -connected peers. - -When sending TCP data, a 'ZMQ_STREAM' socket shall remove the first part of the -message and use it to determine the _identity_ of the peer the message shall be -routed to, and unroutable messages shall cause an EHOSTUNREACH or EAGAIN error. - -To open a connection to a server, use the zmq_connect call, and then fetch the -socket identity using the ZMQ_IDENTITY zmq_getsockopt call. - -To close a specific client connection, as a server, send the identity frame -followed by a zero-length message (see EXAMPLE section). - -The ZMQ_MSGMORE flag is ignored on data frames. You must send one identity frame -followed by one data frame. - -Also, please note that omitting the ZMQ_MSGMORE flag will prevent sending further -data (from any client) on the same socket. - -[horizontal] -.Summary of ZMQ_STREAM characteristics -Compatible peer sockets:: none. -Direction:: Bidirectional -Send/receive pattern:: Unrestricted -Outgoing routing strategy:: See text -Incoming routing strategy:: Fair-queued -Action in mute state:: EAGAIN - - -RETURN VALUE ------------- -The _zmq_socket()_ function shall return an opaque handle to the newly created -socket if successful. Otherwise, it shall return NULL and set 'errno' to one of -the values defined below. - - -ERRORS ------- -*EINVAL*:: -The requested socket 'type' is invalid. -*EFAULT*:: -The provided 'context' is invalid. -*EMFILE*:: -The limit on the total number of open 0MQ sockets has been reached. -*ETERM*:: -The context specified was terminated. - -EXAMPLE -------- -.Creating a simple HTTP server using ZMQ_STREAM ----- -void *ctx = zmq_ctx_new (); -assert (ctx); -/* Create ZMQ_STREAM socket */ -void *socket = zmq_socket (ctx, ZMQ_STREAM); -assert (socket); -int rc = zmq_bind (socket, "tcp://*:8080"); -assert (rc == 0); -/* Data structure to hold the ZMQ_STREAM ID */ -uint8_t id [256]; -size_t id_size = 256; -while (1) { - /* Get HTTP request; ID frame and then request */ - id_size = zmq_recv (server, id, 256, 0); - assert (id_size > 0); - /* Prepares the response */ - char http_response [] = - "HTTP/1.0 200 OK\r\n" - "Content-Type: text/plain\r\n" - "\r\n" - "Hello, World!"; - /* Sends the ID frame followed by the response */ - zmq_send (socket, id, id_size, ZMQ_SNDMORE); - zmq_send (socket, http_response, strlen (http_response), ZMQ_SNDMORE); - /* Closes the connection by sending the ID frame followed by a zero response */ - zmq_send (socket, id, id_size, ZMQ_SNDMORE); - zmq_send (socket, 0, 0, ZMQ_SNDMORE); - /* NOTE: If we don't use ZMQ_SNDMORE, then we won't be able to send more */ - /* message to any client */ -} -zmq_close (socket); -zmq_ctx_destroy (ctx); ----- - - -SEE ALSO --------- -linkzmq:zmq_init[3] -linkzmq:zmq_setsockopt[3] -linkzmq:zmq_bind[3] -linkzmq:zmq_connect[3] -linkzmq:zmq_send[3] -linkzmq:zmq_recv[3] -linkzmq:zmq_inproc[7] -linkzmq:zmq[7] - - -AUTHORS -------- -This page was written by the 0MQ community. To make a change please -read the 0MQ Contribution Policy at <http://www.zeromq.org/docs:contributing>. |