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Diffstat (limited to 'docs/man/nng.7.adoc')
| -rw-r--r-- | docs/man/nng.7.adoc | 83 |
1 files changed, 55 insertions, 28 deletions
diff --git a/docs/man/nng.7.adoc b/docs/man/nng.7.adoc index ee120774..507ddeec 100644 --- a/docs/man/nng.7.adoc +++ b/docs/man/nng.7.adoc @@ -73,46 +73,73 @@ other languages please check the http://nanomsg.org/[website]. == 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. +_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, <<nng_sub.7#,nng_sub(7)>> sockets automatically filter incoming +supports it, and implements the appropriate protocol semantics. +For example, <<nng_sub.7#,_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 -<<nng_req.7#,nng_req(7)>> may offer stronger guarantees by -performing their own retry and validation schemes.) +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 <<nng_req.7#,_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 bind and watch for 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 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. +_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))) +=== Raw Mode + +(((cooked mode))) +Most applications will use _nng_ sockets in "`cooked`" mode. +This mode provides the full semantics of the protocol. +For example, <<nng_req.7#,_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 <<nng_device.7#,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 <<nng_req_open.3#,`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 <<nng_device.3#,`nng_device()`>> function only works with raw mode +sockets, but as it only forwards the messages, no additional application +processing is needed. + === URLs (((URL))) |
