= nng(7) // // Copyright 2019 Staysail Systems, Inc. // Copyright 2018 Capitar IT Group BV // // This document is supplied under the terms of the MIT License, a // copy of which should be located in the distribution where this // file was obtained (LICENSE.txt). A copy of the license may also be // found online at https://opensource.org/licenses/MIT. // == NAME nng - nanomsg next generation == SYNOPSIS *cc* ['flags'] 'files' *-lnng* ['libraries'] == DESCRIPTION The _nng_ library provides a common messaging framework intended to solve common communication problems in distributed applications. It offers a number of _protocols_, and also a number of _transports_. The _protocols_ implement the semantics associated with particular communications scenarios, such as RPC style services, service discovery, publish/subscribe, and so forth. The _transports_ provide support for underlying transport methods, such as TCP, IPC, websockets, and so forth. The _nng_ library is designed to permit easy creation of new _transports_ and, to a lesser extent, new _protocols_. The _nng_ library is wire compatible with the SP protocols described in the nanomsg project; projects using https://github.com/nanomsg/nanomsg[_libnanomsg_] can inter-operate with nng as well as other conforming implementations. (One such implementation is https://github.com/go-mangos/mangos[_mangos_].) Applications using _nng_ which wish to communicate with older libraries must ensure that they only use protocols or transports offered by the earlier library. The _nng_ library also offers a compatible API, permitting legacy code to be recompiled or relinked against _nng_. When doing this, support for certain enhancements or features will likely be absent, requiring the application developer to use the new-style API. The _nng_ library is implemented in pure C; if you need bindings for other languages please check the http://nanomsg.org/[website]. == Protocols [horizontal] xref:nng_bus.7.adoc[nng_bus(7)]:: Bus protocol xref:nng_pair.7.adoc[nng_pair(7)]:: Pair protocol xref:nng_pub.7.adoc[nng_pub(7)]:: Publisher side of publish/subscribe protocol xref:nng_pull.7.adoc[nng_pull(7)]:: Pull side of pipeline protocol xref:nng_push.7.adoc[nng_push(7)]:: Push side of pipeline protocol xref:nng_sub.7.adoc[nng_sub(7)]:: Subscriber side of publish/subscribe protocol xref:nng_rep.7.adoc[nng_rep(7)]:: Reply side of request/reply protocol xref:nng_req.7.adoc[nng_req(7)]:: Request side of request/reply protocol xref:nng_respondent.7.adoc[nng_respondent(7)]:: Respondent side of survey protocol xref:nng_surveyor.7.adoc[nng_surveyor(7)]:: Surveyor side of survey protocol //* xref:nng_bus.7.adoc[nng_bus(7)] - Bus protocol //* xref:nng_pair.7.adoc[nng_pair(7)] - Pair protocol //* xref:nng_pub.7.adoc[nng_pub(7)] - Publisher side of publish/subscribe protocol //* xref:nng_pull.7.adoc[nng_pull(7)] - Pull side of pipeline protocol //* xref:nng_push.7.adoc[nng_push(7)] - Push side of pipeline protocol //* xref:nng_sub.7.adoc[nng_sub(7)] - Subscriber side of publish/subscribe protocol //* xref:nng_rep.7.adoc[nng_rep(7)] - Reply side of request/reply protocol //* xref:nng_req.7.adoc[nng_req(7)] - Request side of request/reply protocol //* xref:nng_respondent.7.adoc[nng_respondent(7)] - Respondent side of survey protocol //* xref:nng_surveyor.7.adoc[nng_surveyor(7)] - Surveyor side of survey protocol == Transports [horizontal] xref:nng_inproc.7.adoc[nng_inproc(7)]:: Intra-process transport xref:nng_ipc.7.adoc[nng_ipc(7)]:: Inter-process transport xref:nng_tls.7.adoc[nng_tls(7)]:: TLSv1.2 over TCP transport xref:nng_tcp.7.adoc[nng_tcp(7)]:: TCP (and TCPv6) transport xref:nng_ws.7.adoc[nng_ws(7)]:: WebSocket transport xref:nng_zerotier.7.adoc[nng_zerotier(7)]:: ZeroTier transport == Conceptual Overview _nng_ presents a _socket_ view of networking. The sockets are constructed using protocol-specific functions, as a given socket implements precisely one _nng_ protocol. Each socket can be used to send and receive messages (if the protocol) supports it, and implements the appropriate protocol semantics. For example, xref:nng_sub.7.adoc[_sub_] sockets automatically filter incoming messages to discard those for topics that have not been subscribed. _nng_ sockets are message oriented, so that messages are either delivered wholly, or not at all. Partial delivery is not possible. Furthermore, _nng_ does not provide any other delivery or ordering guarantees; messages may be dropped or reordered (Some protocols, such as xref:nng_req.7.adoc[_req_] may offer stronger guarantees by performing their own retry and validation schemes.) Each socket can have zero, one, or many "endpoints", which are either _listeners_ or _dialers_. (A given socket may freely choose whether it uses listeners, dialers, or both.) These "`endpoints`" provide access to underlying transports, such as TCP, etc. Each endpoint is associated with a URL, which is a service address. For dialers, this will be the service address that will be contacted, whereas for listeners this is where the listener will accept new connections. Endpoints do not themselves transport data. They are instead responsible for the creation of _pipes_, which can be thought of as message-oriented connected streams. Pipes frequently correspond to a single underlying byte stream. For example both IPC and TCP transports implement their pipes using a 1:1 relationship with a connected operating system socket. Endpoints create pipes as needed. Listeners will create them when a new client connection request arrives, and dialers will generally create one, then wait for it to disconnect before reconnecting. Most applications should not have to worry about endpoints or pipes at all; the socket abstraction should provide all the functionality needed other than in a few specific circumstances. [[raw_mode]] === Raw Mode (((cooked mode)))(((raw mode))) Most applications will use _nng_ sockets in "`cooked`" mode. This mode provides the full semantics of the protocol. For example, xref:nng_req.7.adoc[_req_] sockets will automatically match a reply to a request, and resend requests periodically if no reply was received. There are situations, such as with xref:nng_device.3.adoc[proxies], where it is desirable to bypass these semantics and simply pass messages to and from the socket with no extra semantic handling. This is possible using "`raw`" mode sockets. Raw mode sockets are generally constructed with a different function, such as xref:nng_req_open.3.adoc[`nng_req0_open_raw()`]. Using these sockets, the application can simply send and receive messages, and is responsible for supplying any additional socket semantics. Typically this means that the application will need to inspect message headers on incoming messages, and supply them on outgoing messages. TIP: The xref:nng_device.3.adoc[`nng_device()`] function only works with raw mode sockets, but as it only forwards the messages, no additional application processing is needed. === URLs (((URL))) The _nng_ library uses ((universal resource locators)) (URLs) following the format specified in https://tools.ietf.org/html/rfc3986[RFC 3986], including some schemes that are unique to SP. (((URL, canonicalized))) The URLs used in _nng_ are canonicalized as follows, mostly in accordance with https://tools.ietf.org/html/rfc3986#section-6.2.2[RFC 3986 6.2.2]: . The URL is parsed into scheme, userinfo, host, port, path, query and fragment components. (Not all of these members are necessarily present.) . The scheme, hostname, and port if present, are converted to lower case. . Percent-encoded values for https://tools.ietf.org/html/rfc3986#section-2.3[unreserved characters] converted to their unencoded forms. . Additionally URL percent-encoded values for characters in the path and with numeric values larger than 127 (i.e. not ASCII) are decoded. . The resulting path is checked for invalid UTF-8 sequences, consisting of surrogate pairs, illegal byte sequences, or overlong encodings. If this check fails, then the entire URL is considered invalid. . Path segments consisting of `.` and `..` are resolved as per https://tools.ietf.org/html/rfc3986#section-6.2.2.3[RFC 3986 6.2.2.3]. . Further, empty path segments are removed, meaning that duplicate slash (`/`) separators are removed from the path. Note that steps 4, 5, and 7 are not specified by RFC 3986, but performing them is believed to improve both the usability and security of _nng_ applications, without violating RFC 3986 itself. TIP: Port numbers may be service names in some instances, but it is recommended that numeric port numbers be used when known. If service names are used, it is recommended that they follow the naming conventions for C identifiers, and not be longer than 32 characters in length. This will maximize compatibility across systems and minimize opportunities for confusion when they are parsed on different systems. == API The library API is documented at xref:libnng.3.adoc[libnng(3)]. == SEE ALSO [.text-left] xref:libnng.3.adoc[libnng(3)], xref:nng_compat.3compat.adoc[nng_compat(3compat)]