--- name: "nng_socket_get" section: "3" platform: "linux" package: "libnng-dev" version: "1.10.1-2" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/nng_socket_get" --- # nng\_socket\_get(3) get socket option ## NAME nng\_socket\_get - get socket option ## SYNOPSIS ``` #include int nng_socket_get(nng_socket s, const char *opt, void *val, size_t *valszp); int nng_socket_get_bool(nng_socket s, const char *opt, bool *bvalp); int nng_socket_get_int(nng_socket s, const char *opt, int *ivalp); int nng_socket_get_size(nng_socket s, const char *opt, size_t *zp); int nng_socket_get_uint64(nng_socket s, const char *opt, uint64_t *u64p); int nng_socket_get_string(nng_socket s, const char *opt, char **strp); int nng_socket_get_ptr(nng_socket s, const char *opt, void **ptr); int nng_socket_get_ms(nng_socket s, const char *opt, nng_duration *durp); ``` ## DESCRIPTION The `nng_socket_get()` functions are used to retrieve option values for the socket *s*. The actual options that may be retrieved in this way vary. A number of them are documented in [nng\_options(5)](/nng_options/5.md). Additionally protocol-specific options are documented with the protocols themselves. **Important**\ Access to transport options via this function is deprecated, and may be removed from a future release. Applications should instead make use of nng\_dialer\_get or nng\_listener\_get for specific dialers or listeners. ### Forms In all of these forms, the option *opt* is retrieved from the socket *s*. The forms vary based on the type of the option they take. The details of the type, size, and semantics of the option will depend on the actual option, and will be documented with the option itself. `nng_socket_get()` This function is untyped and can be used to retrieve the value of any option. The caller must store a pointer to a buffer to receive the value in *val*, and the size of the buffer shall be stored at the location referenced by *valszp*. When the function returns, the actual size of the data copied (or that would have been copied if sufficient space were present) is stored at the location referenced by *valszp*. If the caller’s buffer is not large enough to hold the entire object, then the copy is truncated. Therefore the caller should check for truncation by verifying that the returned size in *valszp* does not exceed the original buffer size. It is acceptable to pass `NULL` for *val* if the value in *valszp* is zero. This can be used to determine the size of the buffer needed to receive the object. **Tip**\ It may be easier to use one of the typed forms of this function. `nng_socket_get_bool()` This function is for options which take a Boolean (`bool`). The value will be stored at *bvalp*. `nng_socket_get_int()` This function is for options which take an integer (`int`). The value will be stored at *ivalp*. `nng_socket_get_ms()` This function is used to retrieve time durations (such as timeouts), stored in *durp* as a number of milliseconds. (The special value `NNG_DURATION_INFINITE` means an infinite amount of time, and the special value `NNG_DURATION_DEFAULT` means a context-specific default.) `nng_socket_get_ptr()` This function is used to retrieve a pointer, *ptr*, to structured data. The data referenced by *ptr* is generally managed using other functions. Note that this form is somewhat special in that the object is generally not copied, but instead the **pointer** to the object is copied. `nng_socket_get_size()` This function is used to retrieve a size into the pointer *zp*, typically for buffer sizes, message maximum sizes, and similar options. `nng_socket_get_string()` This function is used to retrieve a string into *strp*. This string is created from the source using `nng_strdup()` and consequently must be freed by the caller using `nng_strfree()` when it is no longer needed. `nng_socket_get_uint64()` This function is used to retrieve a 64-bit unsigned value into the value referenced by *u64p*. This is typically used for options related to identifiers, network numbers, and similar. ## RETURN VALUES These functions return 0 on success, and non-zero otherwise. ## ERRORS `NNG_EBADTYPE` Incorrect type for option. `NNG_ECLOSED` Parameter *s* does not refer to an open socket. `NNG_EINVAL` Size of destination *val* too small for object. `NNG_ENOMEM` Insufficient memory exists. `NNG_ENOTSUP` The option *opt* is not supported. `NNG_EWRITEONLY` The option *opt* is write-only. ## SEE ALSO [nng\_dialer\_get(3)](/nng_dialer_get/3.md), [nng\_listener\_get(3)](/nng_listener_get/3.md), [nng\_pipe\_get(3)](/nng_pipe_get/3.md), [nng\_socket\_set(3)](/nng_socket_set/3.md), [nng\_strdup(3)](/nng_strdup/3.md), [nng\_strerror(3)](/nng_strerror/3.md), [nng\_strfree(3)](/nng_strfree/3.md), [nng\_duration(5)](/nng_duration/5.md), [nng\_options(5)](/nng_options/5.md), [nng\_socket(5)](/nng_socket/5.md), [nng(7)](/nng/7.md)