#include <nng/nng.h>
#define NNG_OPT_RECVBUF "recv-buffer"
#define NNG_OPT_SENDBUF "send-buffer"
#define NNG_OPT_RECVTIMEO "recv-timeout"
#define NNG_OPT_SENDTIMEO "send-timeout"
#define NNG_OPT_LOCADDR "local-address"
#define NNG_OPT_REMADDR "remote-address"
#define NNG_OPT_URL "url"
#define NNG_OPT_MAXTTL "ttl-max"
#define NNG_OPT_RECVMAXSZ "recv-size-max"
#define NNG_OPT_RECONNMINT "reconnect-time-min"
#define NNG_OPT_RECONNMAXT "reconnect-time-max"
#define NNG_OPT_PEER_GID "ipc:peer-gid"
#define NNG_OPT_PEER_PID "ipc:peer-pid"
#define NNG_OPT_PEER_UID "ipc:peer-uid"
#define NNG_OPT_PEER_ZONEID "ipc:peer-zoneid"This page documents the various standard options that can be set or retrieved on objects.
Sockets (nng_socket objects) use the functions
nng_socket_get()
and nng_socket_set() to set and retrieve option values.
Dialers (nng_dialer objects) use the functions
nng_dialer_get() and
nng_dialer_set() to set and retrieve option
values.
Listeners (nng_listener objects) use the functions
nng_listener_get()
and nng_listener_set() to set and
retrieve option values.
Pipes (nng_pipe objects) can only retrieve option values using
the nng_pipe_get() function.
Other object types may have additional methods to access these options.
In addition to the options listed here, transports and protocols will generally have some of their own options, which will be documented with the transport or protocol.
In the following list of options, the name of the option is supplied, along with the data type of the underlying value.
Some options are only meaningful or supported in certain contexts; for example there is no single meaningful address for a socket, since sockets can have multiple dialers and endpoints associated with them. An attempt has been made to include details about such restrictions in the description of the option.
NNG_OPT_LOCADDR-
(
nng_sockaddr) This read-only option may be used on listeners, dialers and connected pipes, and represents the local address used for communication. NOTE: Not all transports support this option, and some transports may support it on listeners but not dialers.When used on a TCP dialer, this option is used to configure the source IP address that will be used when initiating outgoing connections. The specific port number will be ignored, however, and the system will choose a random ephemeral port instead.
NNG_OPT_RAW-
(
bool) This read-only option indicates whether the socket is in raw mode. Iftrue, the socket is in raw mode, and iffalsethe socket is in normal mode.Raw mode sockets generally do not have any protocol-specific semantics applied to them; instead the application is expected to perform such semantics itself. (For example, in normal mode a rep socket would automatically copy message headers from a received message to the corresponding reply, whereas in raw mode this is not done.) See Raw Mode for more details.
NNG_OPT_RECONNMINT-
(
nng_duration) This is the minimum amount of time (milliseconds) to wait before attempting to establish a connection after a previous attempt has failed. This can be set on a socket, but it can also be overridden on an individual dialer. The option is irrelevant for listeners.
NNG_OPT_RECONNMAXT-
(
nng_duration) This is the maximum amount of time (milliseconds) to wait before attempting to establish a connection after a previous attempt has failed. If this is non-zero, then the time between successive connection attempts will start at the value ofNNG_OPT_RECONNMINT, and grow exponentially, until it reaches this value. If this value is zero, then no exponential back-off between connection attempts is done, and each attempt will wait the time specified byNNG_OPT_RECONNMINT. This can be set on a socket, but it can also be overridden on an individual dialer. The option is irrelevant for listeners.
NNG_OPT_RECVBUF-
(
int) This is the depth of the socket’s receive buffer as a number of messages. Messages received by a transport may be buffered until the application has accepted them for delivery. This value must be an integer between 0 and 8192, inclusive. NOTE: Not all protocols support buffering received messages. For example req can only deal with a single reply at a time.
NNG_OPT_RECVMAXSZ-
(
size_t) This is the maximum message size that the will be accepted from a remote peer. If a peer attempts to send a message larger than this, then the message will be discarded. If the value of this is zero, then no limit on message sizes is enforced. This option exists to prevent certain kinds of denial-of-service attacks, where a malicious agent can claim to want to send an extraordinarily large message, without sending any data. This option can be set for the socket, but may be overridden for on a per-dialer or per-listener basis.ImportantApplications on hostile networks should set this to a non-zero value to prevent denial-of-service attacks. ImportantThis option should be set before any listeners or dialers are added. Ideally this option should be set on specific dialers or listeners; setting it on the socket globally is deprecated behavior, and might not work in a future release, or might only work for endpoints that have not yet been created. (Maximum receive sizes might be negotiated during connection establishment for future transports, which means that the option needs to be set before any connections are established.) NoteSome transports may have further message size restrictions.
NNG_OPT_RECVTIMEO-
(
nng_duration) This is the socket receive timeout in milliseconds. When no message is available for receiving at the socket for this period of time, receive operations will fail with a return value ofNNG_ETIMEDOUT.
NNG_OPT_REMADDR-
(
nng_sockaddr) This read-only option may be used on dialers and connected pipes, and represents the address of a remote peer. Not all transports support this option.
NNG_OPT_SENDBUF-
(
int) This is the depth of the socket send buffer as a number of messages. Messages sent by an application may be buffered by the socket until a transport is ready to accept them for delivery. This value must be an integer between 0 and 8192, inclusive.NoteNot all protocols support buffering sent messages. For example, req can only have a single request outstanding at a time (per context).
NNG_OPT_SENDTIMEO-
(
nng_duration) This is the socket send timeout in milliseconds. When a message cannot be queued for delivery by the socket for this period of time (such as if send buffers are full), the operation will fail with a return value ofNNG_ETIMEDOUT.
NNG_OPT_MAXTTL-
(
int) This is the maximum number of times a message may traverse across anng_device()forwarders. The intention here is to prevent forwarding loops in device chains. When this is supported, it can have a value between 1 and 255, inclusive.NoteNot all protocols support this option. Those that do generally have a default value of 8. TipEach node along a forwarding path may have its own value for the maximum time-to-live, and performs its own checks before forwarding a message. Therefore it is helpful if all nodes in the topology use the same value for this option.
NNG_OPT_URL-
(string) This read-only option is used to obtain the URL with which a listener or dialer was configured. Accordingly it can only be used with dialers, listeners, and pipes.
NoteSome transports will canonify URLs before returning them to the application.
NNG_OPT_PEER_GID-
(
uint64_t) This read-only option provides a connected peer’s primary group id, when known. This is the effective group id of the peer when either the underlyinglisten()orconnect()calls were made, and is not forgeable. This option is generally only available on POSIX systems, only on certain transports.
NNG_OPT_PEER_PID-
(
uint64_t) This read-only option provides the process id of the connected peer, when known. This option is only available on certain platforms and transports.NoteApplications should not assume that the process ID does not change, as it may be possible for a process to pass a file descriptor between processes. However, it is not possible for a nefarious application to forge the identity of a well-behaved one using this method.
NNG_OPT_PEER_UID-
(
uint64_t) This read-only option provides a connected peer’s user id. This is the effective user id of the peer when either the underlyinglisten()orconnect()calls were made, and cannot be forged. This option is generally only available on POSIX systems, on certain transports.
NNG_OPT_PEER_ZONEID-
(
uint64_t) This read-only option provides a connected peer’s the zone id. Zones (and this option) are only supported on Solaris and illumos systems, on select transports.