## nng_ctx_set

Set context option.

### Synopsis

```c
#include <nng/nng.h>

int nng_ctx_set(nng_ctx ctx, const char *opt, const void *val, size_t valsz);

int nng_ctx_set_bool(nng_ctx ctx, const char *opt, int bval);
int nng_ctx_set_int(nng_ctx ctx, const char *opt, int ival);
int nng_ctx_set_ms(nng_ctx ctx, const char *opt, nng_duration dur);
int nng_ctx_set_size(nng_ctx ctx, const char *opt, size_t z);
int nng_ctx_set_string(nng_ctx ctx, const char *opt, const char *str);
int nng_ctx_set_uint64(nng_ctx ctx, const char *opt, uint64_t u64);
```

### Description

(((options, context)))
The `nng_ctx_set` functions are used to configure options for the context _ctx_.
The actual options that may be configured in this way vary, and are specified by _opt_.

TIP: Context options are protocol specific.
See the option documentation for more information.

#### Forms

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.

TIP: It is recommended to use one of the typed forms of this function instead of `nng_set`, when possible.

`nng_ctx_set`::
This function is untyped, and can be used to configure any arbitrary data.
The _val_ pointer addresses the data to copy, and _valsz_ is the size of the objected located at _val_.

`nng_ctx_set_bool`::
This function sets a Boolean (`bool`) option to _bval_.

`nng_ctx_set_int`::
This function sets an integer (`int`) option to _ival_.

`nng_ctx_set_ms`::
This function sets a duration (xref:nng_duration.adoc[`nng_duration`]) option to _dur_, which is an integer number of milliseconds.

`nng_ctx_set_size`::
This function sets a size (`size_t`) option to _z_.

`nng_ctx_set_string`::
This function sets a string (`const char *`) option to _str_.
Strings must be legal UTF-8, terminated with a `NUL` (`\0`) byte.

`nng_ctx_set_uint64`::
This function sets a 64-bit unsigned integer (`uint64_t`) option to _u64_.

### Return Values

These functions return 0 on success, and non-zero otherwise.

### Errors

[horizontal]
`NNG_ECLOSED`:: Parameter _s_ does not refer to an open socket.
`NNG_EINVAL`:: The value being passed is invalid.
`NNG_ENOTSUP`:: The option _opt_ is not supported.
`NNG_EREADONLY`:: The option _opt_ is read-only.
`NNG_ESTATE`:: The socket is in an inappropriate state for setting this option.

### See Also

xref:../opts/index.adoc[Options],
xref:nng_ctx_get.adoc[nng_ctx_get],
xref:nng_socket_set.adoc[nng_socket_set]