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diff --git a/docs/ref/api/http.md b/docs/ref/api/http.md new file mode 100644 index 00000000..b2382155 --- /dev/null +++ b/docs/ref/api/http.md @@ -0,0 +1,572 @@ +# HTTP Support + +NNG offers support for creation of HTTP clients, and servers. NNG supports HTTP/1.1 at present, and supports +a subset of functionality, but the support should be sufficient for simple clients, REST API servers, static content servers, +and gateways between HTTP and and other protocols. It also provides support for WebSocket based connections. + +HTTP follows a request/reply model, where a client issues a request, and the server is expected to reply. +Every request is answered with a single reply. + +## Header File + +```c +#include <nng/http.h> +``` + +Unlike the rest of NNG, the HTTP API in NNG requires including `nng/http.h`. It is not necessary to include +the main `nng/nng.h` header, it will be included transitively by `nng/http.h`. + +## Connection Object + +```c +typedef struct nng_http nng_http; +``` + +The {{i:`nng_http`}} object represents a single logical HTTP connection to the server. +For HTTP/1.1 and earlier, this will correspond to a single TCP connection, but the object +also contains state relating to the transaction, such as the hostname used, HTTP method used, +request headers, response status, response headers, and so forth. + +An `nng_http` object can be reused, unless closed, so that additional transactions can be +performed after the first transaction is complete. + +At any given point in time, an `nng_http` object can only refer to a single HTTP transaction. +In NNG, these `nng_http` objects are used in both the client and server APIs. + +The `nng_http` object is created by either [`nng_http_client_connect`] or by an HTTP server +object which then passes it to an [`nng_http_handler`] callback function. + +### HTTP Method + +```c +void nng_http_set_method(nng_http *conn, const char *method); +const char *nng_http_get_method(nng_http *conn); +``` + +Each HTTP transaction has a single verb, or method, that is used. The most common methods are "GET", "HEAD", and "POST", +but a number of others are possible. + +The {{i:`nng_http_set_method`}} function specifies the HTTP method to use for the transaction. +The default is "GET". HTTP methods are case sensitive, and generally upper-case, such as "GET", "POST", "HEAD", +and so forth. This function silently truncates any method to 32-characters. (There are no defined methods longer than this.) + +The {{i:`nng_http_get_method`}} function is used, typically on a server, to retrieve the method the client +set when issuing the transaction. + +### HTTP URI + +```c +int nng_http_set_uri(nng_http *conn, const char *uri, const char *query); +const char *nng_http_get_uri(nng_http *conn); +``` + +The {{i:`nng_http_set_uri`}} function sets the {{i:URI}}, which normally appears like a path such as "/docs/index.html", +for the next transaction on _conn_. It sets the URI to _uri_, and, if _query_ is not `NULL`, also appends the +contents of _query_, separated by either the '?' or '&' character, depending on whether _uri_ already +contains a query string. It may return [`NNG_ENOMEM`], or [`NNG_EMSGSIZE`] if the the result is too long, +or [`NNG_EINVAL`] if there is some other problem with the URI. + +> [!NOTE] +> The _uri_ and _query_ must be already percent-encoded if necessary. + +The {{i:`nni_http_get_uri`}} function is used to obtain the URI that was previously set by `nng_http_set_uri`. +If the URI is unset (such as for a freshly created connection), then it returns `NULL`. The returned value +will have any query concentated, for example "/api/get_user.cgi?name=garrett". + +### HTTP Version + +```c +int nng_http_set_version(nng_http *conn, const char *version); +const char *nng_http_get_version(nng_http *conn); +``` + +The {{i:`nng_http_set_version`}} function is used to select the HTTP protocol version to use for the +exchange. At present, only the values `NNG_HTTP_VERSION_1_0` and `NNG_HTTP_VERSION_1_1` (corresponding to +"HTTP/1.0" and "HTTP/1.1") are supported. NNG will default to using "HTTP/1.1" if this function is not called. +If an unsupported version is supplied, [`NNG_ENOTSUP`] will be returned, otherwise zero. + +The {{i:`nng_http_get_version`}} function is used to determine the version the client selected. Normally +there is little need to use this, but there are some subtle semantic differences between HTTP/1.0 and HTTP/1.1. + +> [!TIP] +> There are few, if any, remaining HTTP/1.0 implementations that are not also capable of HTTP/1.1. +> It might be easiest to just fail any request coming in that is not HTTP/1.1. + +> [!NOTE] +> NNG does not support HTTP/2 or HTTP/3 at this time. + +### HTTP Status + +```c +uint16_t nng_http_get_status(nng_http *conn); +const char *nng_http_get_reason(nng_http_conn *conn); +void nng_http_set_status(nng_http *conn, uint16_t status, const char *reason); +``` + +The {{i:`nng_http_get_status`}} function obtains the numeric code (typipcally numbered from 100 through 599) returned +by the server in the last exchange on _conn_. (If no exchange has been performed yet, the result is undefined.) + +A descriptive message matching the status code is returned by {{i:`nng_http_get_reason`}}. + +The {{i:`nng_http_set_status`}} function is used on a server in a handler callback to set the status codethat will be +reported to the client to _status_, and the associated text (reason) to _reason_. If _reason_ is `NULL`, +then a built in reason based on the _status_ will be used instead. + +> [!TIP] +> Callbacks used on the server may wish to use [`nng_http_server_set_error`] or [`nng_http_server_set_redirect`] instead of +> `nng_http_set_status`, because those functions will also set the response body to a suitable HTML document +> for display to users. + +Status codes are defined by the IETF. Here are defininitions that NNG provides for convenience: + +| Name | Code | Reason Text | Notes | +| ------------------------------------------------------------------------------------------------ | ---- | ------------------------------- | ----------------------------------------------------- | +| `NNG_HTTP_STATUS_CONTINUE`<a name="#NNG_HTTP_STATUS_CONTINUE"></a> | 100 | Continue | Partial transfer, client may send body. | +| `NNG_HTTP_STATUS_SWITCHING`<a name="#NNG_HTTP_STATUS_SWITCHING"></a> | 101 | Switching Protocols | Used when upgrading or hijacking a connection. | +| `NNG_HTTP_STATUS_PROCESSING`<a name="#NNG_HTTP_STATUS_PROCESSING"></a> | 102 | Processing | +| `NNG_HTTP_STATUS_OK`<a name="#NNG_HTTP_STATUS_OK"></a> | 200 | OK | Successful result. | +| `NNG_HTTP_STATUS_CREATED`<a name="#NNG_HTTP_STATUS_CREATED"></a> | 201 | Created | Resource created successfully. | +| `NNG_HTTP_STATUS_ACCEPTED`<a name="#NNG_HTTP_STATUS_ACCEPTED"></a> | 202 | Created | Request accepted for future processing. | +| `NNG_HTTP_STATUS_NOT_AUTHORITATIVE`<a name="#NNG_HTTP_STATUS_NOT_AUTHORITATIVE"></a> | 203 | Not Authoritative | Request successful, but modified by proxy. | +| `NNG_HTTP_STATUS_NO_CONTENT`<a name="#NNG_HTTP_STATUS_NO_CONTENT"></a> | 204 | No Content | Request successful, no content returned. | +| `NNG_HTTP_STATUS_RESET_CONTENT`<a name="#NNG_HTTP_STATUS_NO_CONTENT"></a> | 205 | Reset Content | Request successful, client should reload content. | +| `NNG_HTTP_STATUS_PARTIAL_CONTENT`<a name="#NNG_HTTP_STATUS_NO_CONTENT"></a> | 206 | Partial Content | Response to a range request. | +| `NNG_HTTP_STATUS_MULTI_STATUS`<a name="#NNG_HTTP_STATUS_MULTI_STATUS"></a> | 207 | Multi-Status | Used with WebDAV. | +| `NNG_HTTP_STATUS_ALREADY_REPORTED`<a name="#NNG_HTTP_STATUS_ALREADY_REPORTED"></a> | 208 | Already Reported | Used with WebDAV. | +| `NNG_HTTP_STATUS_IM_USED`<a name="#NNG_HTTP_STATUS_IM_USED"></a> | 226 | IM Used | Used with delta encodings, rarely supported. | +| `NNG_HTTP_STATUS_MULTIPLE_CHOICES`<a name="#NNG_HTTP_STATUS_MULTIPLE_CHOICES"></a> | 300 | Multiple Choices | Multiple responses possible, client should choose. | +| `NNG_HTTP_STATUS_MOVED_PERMANENTLY`<a name="#NNG_HTTP_STATUS_MOVED_PERMANENTLY"></a> | 301 | Moved Permanently | Permanent redirection, may be saved by client. | +| `NNG_HTTP_STATUS_FOUND`<a name="#NNG_HTTP_STATUS_FOUND"></a> | 302 | Found | Temporary redirection, client may switch to GET. | +| `NNG_HTTP_STATUS_SEE_OTHER`<a name="#NNG_HTTP_STATUS_SEE_OTHER"></a> | 303 | See Other | Redirect, perhaps after a success POST or PUT. | +| `NNG_HTTP_STATUS_NOT_MODIFIED`<a name="#NNG_HTTP_STATUS_NOT_MODIFIED"></a> | 304 | Not Modified | Resource not modified, client may use cached version. | +| `NNG_HTTP_STATUS_USE_PROXY`<a name="#NNG_HTTP_STATUS_USE_PROXY"></a> | 305 | Use Proxy | +| `NNG_HTTP_STATUS_TEMPORARY_REDIRECT`<a name="#NNG_HTTP_STATUS_TEMPORARY_REDIRECT"></a> | 307 | Temporary Redirect | Temporary redirect, preserves method. | +| `NNG_HTTP_STATUS_PERMANENT_REDIRECT`<a name="#NNG_HTTP_STATUS_PERMANENT_REDIRECT"></a> | 308 | Permanent Redirect | Permanent redirect. | +| `NNG_HTTP_STATUS_BAD_REQUEST`<a name="#NNG_HTTP_STATUS_BAD_REQUEST"></a> | 400 | Bad Request | Generic problem with the request. | +| `NNG_HTTP_STATUS_UNAUTHORIZED`<a name="#NNG_HTTP_STATUS_UNAUTHORIZED"></a> | 401 | Unauthorized | Indicates a problem with authentication. | +| `NNG_HTTP_STATUS_PAYMENT_REQUIRED`<a name="#NNG_HTTP_STATUS_PAYMENT_REQUIRED"></a> | 402 | Payment Required | +| `NNG_HTTP_STATUS_FORBIDDEN`<a name="#NNG_HTTP_STATUS_FORBIDDEN"></a> | 403 | Forbidden | No permission to access resource. | +| `NNG_HTTP_STATUS_NOT_FOUND`<a name="#NNG_HTTP_STATUS_NOT_FOUND"></a> | 404 | Not Found | Resource does not exist. | +| `NNG_HTTP_STATUS_METHOD_NOT_ALLOWED`<a name="#NNG_HTTP_STATUS_METHOD_NOT_ALLOWED"></a> | 405 | Method Not Allowed | Resource does not support the method. | +| `NNG_HTTP_STATUS_METHOD_NOT_ACCEPTABLE`<a name="#NNG_HTTP_STATUS_METHOD_NOT_ACCEPTABLE"></a> | 406 | Not Acceptable | Could not satisfy accept requirements. | +| `NNG_HTTP_STATUS_PROXY_AUTH_REQUIRED`<a name="#NNG_HTTP_STATUS_PROXY_AUTH_REQUIRED"></a> | 407 | Proxy Authentication Required | Proxy requires authentication. | +| `NNG_HTTP_STATUS_REQUEST_TIMEOUT`<a name="#NNG_HTTP_STATUS_REQUEST_TIMEOUT"></a> | 408 | Request Timeout | Timed out waiting for request. | +| `NNG_HTTP_STATUS_CONFLICT`<a name="#NNG_HTTP_STATUS_CONFLICT"></a> | 409 | Conflict | Conflicting request. | +| `NNG_HTTP_STATUS_GONE`<a name="#NNG_HTTP_STATUS_GONE"></a> | 410 | Gone | Resource no longer exists. | +| `NNG_HTTP_STATUS_LENGTH_REQUIRED`<a name="#NNG_HTTP_STATUS_LENGTH_REQUIRED"></a> | 411 | Length Required | Missing Content-Length. | +| `NNG_HTTP_STATUS_PRECONDITION_FAILED`<a name="#NNG_HTTP_STATUS_PRECONDITION_FAILED"></a> | 412 | Precondition Failed | | +| `NNG_HTTP_STATUS_CONTENT_TOO_LARGE`<a name="#NNG_HTTP_STATUS_PAYLOAD_TOO_LARGE"></a> | 413 | Content Too Large | | +| `NNG_HTTP_STATUS_URI_TOO_LONG`<a name="#NNG_HTTP_STATUS_URI_TOO_LONG"></a> | 414 | URI Too Long | | +| `NNG_HTTP_STATUS_UNSUPPORTED_MEDIA_TYPE`<a name="#NNG_HTTP_STATUS_UNSUPPORTED_MEDIA_TYPE"></a> | 415 | Unsupported Media Type | +| `NNG_HTTP_STATUS_RANGE_NOT_SATISFIABLE`<a name="#NNG_HTTP_STATUS_RANGE_NOT_SATISFIABLE"></a> | 416 | Range Not Satisfiable | +| `NNG_HTTP_STATUS_EXPECTATION_FAILED`<a name="#NNG_HTTP_STATUS_EXPECTATION_FAILED"></a> | 417 | Expectation Failed | +| `NNG_HTTP_STATUS_TEAPOT`<a name="#NNG_HTTP_STATUS_TEAPOT"></a> | 418 | I Am A Teapot | RFC 2324. | +| `NNG_HTTP_STATUS_UNPROCESSABLE_ENTITY`<a name="#NNG_HTTP_STATUS_UNPROCESSABLE_ENTITY"></a> | 422 | Unprocessable Entity | +| `NNG_HTTP_STATUS_LOCKED`<a name="#NNG_HTTP_STATUS_LOCKED"></a> | 423 | Locked | +| `NNG_HTTP_STATUS_FAILED_DEPENDENCY`<a name="#NNG_HTTP_STATUS_FAILED_DEPEDNENCY"></a> | 424 | Failed Dependency | +| `NNG_HTTP_STATUS_TOO_EARLY`<a name="#NNG_HTTP_STATUS_TOO_EARLY"></a> | 425 | Too Early | +| `NNG_HTTP_STATUS_UPGRADE_REQUIRED`<a name="#NNG_HTTP_STATUS_UPGRADE_REQUIRED"></a> | 426 | Upgrade Required | +| `NNG_HTTP_STATUS_PRECONDITION_REQUIRED`<a name="#NNG_HTTP_STATUS_PRECONDITION_REQUIRED"></a> | 428 | Precondition Required | | +| `NNG_HTTP_STATUS_TOO_MANY_REQUESTS`<a name="#NNG_HTTP_STATUS_TOO_MANY_REQUESTS"></a> | 429 | Too Many Requests | | +| `NNG_HTTP_STATUS_HEADERS_TOO_LARGE`<a name="#NNG_HTTP_STATUS_HEADERS_TOO_LARGE"></a> | 431 | Headers Too Large | | +| `NNG_HTTP_STATUS_UNAVAIL_LEGAL_REASONS`<a name="#NNG_HTTP_STATUS_UNAVAIL_LEGAL_REASONS"></a> | 451 | Unavailabe For Legal Reasons | | +| `NNG_HTTP_STATUS_INTERNAL_SERVER_ERROR`<a name="#NNG_HTTP_STATUS_INTERNAL_SERVER_ERROR"></a> | 500 | Internal Server Error | +| `NNG_HTTP_STATUS_NOT_IMPLEMENTED`<a name="#NNG_HTTP_STATUS_NOT_IMPLEMENTED"></a> | 501 | Not Implemented | Server does not implement method. | +| `NNG_HTTP_STATUS_BAD_GATEWAY`<a name="#NNG_HTTP_STATUS_BAD_GATEWAY"></a> | 502 | Bad Gateway | +| `NNG_HTTP_STATUS_SERVICE_UNAVAILALE`<a name="#NNG_HTTP_STATUS_SERVICE_UNAVAILABLE"></a> | 503 | Service Unavailable | +| `NNG_HTTP_STATUS_GATEWAY_TIMEOUT`<a name="#NNG_HTTP_STATUS_GATEWAY_TIMEOUT"></a> | 504 | Gateway TImeout | +| `NNG_HTTP_STATUS_HTTP_VERSION_NOT_SUPP`<a name="#NNG_HTTP_STATUS_HTTP_VERSION_NOT_SUPP"></a> | 505 | HTTP Version Not Supported | +| `NNG_HTTP_STATUS_VARIANT_ALSO_NEGOTIATES`<a name="#NNG_HTTP_STATUS_VARIANT_ALSO_NEGOTIATES"></a> | 506 | Variant Also Negotiates | +| `NNG_HTTP_STATUS_INSUFFICIENT_STORAGE`<a name="#NNG_HTTP_STATUS_INSUFFICIENT_STORAGE"></a> | 507 | Variant Also Negotiates | +| `NNG_HTTP_STATUS_LOOP_DETECTED`<a name="#NNG_HTTP_STATUS_LOOP_DETECTED"></a> | 508 | Loop Detected | +| `NNG_HTTP_STATUS_NOT_EXTENDED`<a name="#NNG_HTTP_STATUS_NOT_EXTENDED"></a> | 510 | Not Extended | +| `NNG_HTTP_STATUS_NETWORK_AUTH_REQUIRED`<a name="#NNG_HTTP_STATUS_NETWORK_AUTH_REQUIRED"></a> | 511 | Network Authentication Required | + +### Retrieving Headers + +```c +const char *nng_http_get_header(nng_http *conn, const char *key); +bool nng_next_header(nng_http *conn, const char **keyp, const char **valuep, void **next); +``` + +The {{i:`nng_http_get_header`}} returns the header value matching _key_ that was received over _conn_, +or `NULL` if no such header exists. + +Thus, if _conn_ is a client connection, then this function returns the the header value +sent by the server as part of a response, whereas if it is a server connection, it returns +the header value sent by the client as part of the request. + +If multiple headers are present with the same key, they may be returned as a combined value, +with individual values separated by commas, but this behavior is not guaranteed. + +The {{i:`nng_http_next_header`}} function iterates over all the headers, using the same list +that `nng_http_get_header` uses. To start, it is called with _next_ initialized to `NULL`. +If a header was found, then it returns `true`, and sets _keyp_ and _valuep_ to values containing +the header name and value. It also updates _next_, which should be used for the next iteration. + +Once `nng_http_next_header` returns `false`, further calls with the same parameters will continue to do so. +The scan can be rest by setting _next_ to `NULL`. + +### Modifying Headers + +```c +int nng_http_add_header(nng_http *conn, const char *key, const char *val); +int nng_http_set_header(nng_http *conn, const char *key, const char *val); +void nng_http_del_header(nng_http *conn, const char *key); +``` + +The {{i:`nng_http_add_header`}}, {{i:`nng_http_set_header`}}, and {{i:`nng_http_del_header`}} functions are +used to add a modify either the request or response headers for _conn_ prior to sending to the connected peer on _conn_. + +Thus, if the _conn_ is a client connection created by [`nng_http_client_connect`], then the request headers are modified. +Conversely, if it is a connection created by an HTTP server and used in a callback function, then the response headers are modified. + +The `nng_http_add_header` function adds a header with the name _key_, and the value _val_, to the list of headers. +In so doing, it may bring collapse multiple headers with the same name into a comma separated list, following +the syntax specified in RFC 9110. The function may return [`NNG_ENOMEM`], [`NNG_EMSGSIZE`], or [`NNG_EINVAL`]. + +The `nng_http_set_header` function adds the header if it does not already exist, but replaces any and all previously existing +headers with the same name _key_, if they exist. In all other respects it behaves similarly to `nng_http_add_header`. + +The `nng_http_del_header` removes all headers with name _key_. + +> [!NOTE] +> Some HTTP headers have special semantics, such as the "Host", "Content-Length", and "Content-Type" headers. +> This implementation may apply those semantics, in order to conform to the specifications for HTTP, such +> as by guaranting that only a single instance of one of these headers is present. + +### Retrieving Body Content + +```c +void nng_http_get_body(nng_http_conn *conn, void **datap, size_t *sizep); +``` + +The {{i:`nng_http_get_data`}} obtains the most recently received request or +response body. This will be `NULL` if the content has not been retrieved +properly yet, or if the peer did not any content. (Some requests are defined +to never have body content, such as "HEAD".) + +### Storing Body Content + +```c +void nng_http_set_body(nng_http_conn *conn, void *data, size_t size); +void nng_http_copy_body(nng_http_conn *conn, const void *data, size_t size); +``` + +The {{i:`nng_http_set_data`}} function sets the outgoing body content to _data_, +which must be _size_ bytes long. The caller must ensure that _data_ remains +valid for the duration of the transaction. + +The {{i:`nng_http_copy_data`}} function makes a copy of _data_, which +will be freed automatically when the transaction is finished, but otherwise +behaves like `nng_http_set_data`. + +On client _conn_ objects, these functions update the request object, but on server +_conn_ objects, they update the response object. + +These functions also update the relevant "Content-Length" header. + +> [!NOTE] +> The current framework does not support sending data via chunked +> transfer-encoding. + +> [!TIP] +> It is a good idea to also set the `Content-Type` header. + +### Closing the Connection + +```c +void nng_http_close(nng_http *conn); +``` + +The {{i:`nng_http_close`}} function closes the supplied HTTP connection _conn_, +including any disposing of any underlying file descriptors or related resources. + +Once this function, no further access to the _conn_ structure may be made. + +### Reset Connection State + +```c +void nng_http_reset(nng_http *conn); +``` + +The {{i:`nng_http_reset`}} function resets the request and response state of the +the connection _conn_, so that it is just as if it had been freshly created with +[`nng_http_client_connect`] or passed into a handler function for a server callback. + +The intended purpose of this function is to clear the object state before reusing the _conn_ for +subsequent transactions. + +### Direct Read and Write + +```c +void nng_http_read(nng_http *conn, nng_aio *aio); +void nng_http_write(nng_http *conn, nng_aio *aio); +void nng_http_read_all(nng_http *conn, nng_aio *aio); +void nng_http_write_all(nng_http *conn, nng_aio *aio); +``` + +The {{i:`nng_http_read`}} and {{i:`nng_http_write`}} functions read or write data asynchronously from or to the +connection _conn_, using the [`nng_iov`] that is set in _aio_ with [`nng_aio_set_iov`]. +These functions will complete as soon as any data is transferred. +Use [`nng_aio_count`] to determine how much data was actually transferred. + +The {{i:`nng_http_read_all`}} and {{i:`nng_http_write_all`}} functions perform the same task, but will keep resubmitting +operations until the the entire amount of data requested by the [`nng_iov`] is transferred. + +> [!NOTE] +> These functions perform no special handling for chunked transfers. + +These functions are most likely to be useful after hijacking the connection with [`nng_http_hijack`]. +They can be used to transfer request or response body data as well. + +### Hijacking Connections + +```c +void nng_http_hijack(nng_http_conn *conn); +``` + +TODO: This API will change to convert the conn into a stream object. + +The {{i:`nng_http_hijack`}} function hijacks the connection _conn_, causing it +to be disassociated from the HTTP server where it was created. + +The purpose of this function is the creation of HTTP upgraders (such as +WebSocket), where the underlying HTTP connection will be taken over for +some other purpose, and should not be used any further by the server. + +This function is most useful when called from a handler function. +(See [`nng_http_handler_alloc`].) + +> [!NOTE] +> It is the responsibility of the caller to dispose of the underlying connection when it is no longer needed. +> Furthermore, the HTTP server will no longer send any responses to the hijacked connection, so the caller should do that as well if appropriate. +> (See [`nng_http_write_response`].) + +> [!TIP] +> This function is intended to facilitate uses cases that involve changing the protocol from HTTP, such as WebSocket. +> Most applications will never need to use this function. + +## Client API + +The NNG client API consists of an API for creating connections, and an API for performing +transactions on those connections. + +### Client Object + +```c +typedef struct nng_http_client nng_http_client; +``` + +The {{i:`nng_http_client`}} object is the client side creator for [`nng_http`] objects. +It is analogous to a [dialer] object used elsewhere in NNG, but it specifically is only for HTTP. + +### Create a Client + +```c +void nng_http_client_alloc(nng_http_client *clientp, const nng_url *url); +``` + +The {{i:`nng_http_client_alloc`}} allocates an HTTP client suitable for +connecting to the server identified by _url_ and stores a pointer to +it in the location referenced by _clientp_. + +### Destroy a Client + +```c +void nng_http_client_free(nng_http_client *client); +``` + +The {{i:`nng_http_client_free`}} connection destroys the client object and any +of its resources. + +> [!NOTE] +> Any connections created by [`nng_http_client_connect`] are not affected by this function, +> and must be closed explicitly as needed. + +### Client TLS + +```c +int nng_http_client_get_tls(nng_http_client *client, nng_tls_config **tlsp); +int nng_http_client_set_tls(nng_http_client *client, nng_tls_config *tls); +``` + +The {{i:`nng_http_client_get_tls`}} and {{i:`nng_http_client_set_tls`}} functions are used to +retrieve or change the [TLS configuration][`nng_tls_config`] used when making outbound connections, enabling +{{i:TLS}} as a result. + +If TLS has not been previously configured on _client_, then `nng_http_client_get_tls` will return [`NNG_EINVAL`]. +Both functions will return [`NNG_ENOTSUP`] if either HTTP or TLS is not supported. + +Calling `nng_http_client_set_tls` invalidates any client previously obtained with +`nng_http_client_get_tls`, unless a separate hold on the object was obtained. + +Once TLS is enabled for an `nng_http_client`, it is not possible to disable TLS. + +> [!NOTE] +> The TLS configuration itself cannnot be changed once it has been used to create a connection, +> such as by calling [`nng_http_client_connect`], but a new one can be installed in the client. +> Existing connections will use the TLS configuration that there were created with. + +### Creating Connections + +```c +#include <nng/http.h> + +void nng_http_client_connect(nng_http_client *client, nng_aio *aio); +``` + +The {{i:`nng_http_client_connect`}} function makes an outgoing connection to the +server configured for _client_, and creates an [`nng_http`] object for the connection. + +This is done asynchronously, and when the operation succeseds the connection may be +retried from the _aio_ using [`nng_aio_get_output`] with index 0. + +#### Example 1: Connecting to Google + +```c +nng_aio *aio; +nng_url *url; +nng_http_client *client; +nng_http *conn; +int rv; + +// Error checks elided for clarity. +nng_url_parse(&url, "http://www.google.com"); +nng_aio_alloc(&aio, NULL, NULL); +nng_http_client_alloc(&client, url); + +nng_http_client_connect(client, aio); + +// Wait for connection to establish (or attempt to fail). +nng_aio_wait(aio); + +if ((rv = nng_aio_result(aio)) != 0) { + printf("Connection failed: %s\n", nng_strerror(rv)); +} else { + // Connection established, get it. + conn = nng_aio_get_output(aio, 0); + + // ... do something with it here + + // Close the connection when done to avoid leaking it. + nng_http_close(conn); +} +``` + +### Preparing a Transaction + +```c +int nng_http_set_version(nng_http *conn, const char *version); +int nng_http_set_uri(nng_http *conn, const char *uri); +``` + +The {{i:`nng_http_set_uri`}} function provides a URI for the transaction. This will be used to +set the URI for the request. The URI typically appears like a path, starting with "/", although +it may also contain a query string. + +### Request Body + +### Sending the Request + +```c +void nng_http_write_request(nng_http *conn, nng_aio *aio); +``` + +The {{i:`nng_http_write_request`}} function starts an asynchronous write of +the HTTP request associated with _conn_. +The entire request is sent, +including headers, and if present, the request body data. +(The request body can be set with +[`nng_http_set_data`] or [`nng_http_copy_data`].) + +This function returns immediately, with no return value. +Completion of the operation is signaled via the _aio_, and the final result +may be obtained via [`nng_aio_result`]. + +> [!TIP] +> Consider using the [`nng_http_transact`] function, +> which provides a simpler interface for performing a complete HTTP client transaction. + +## Obtaining the Response + +```c +void nng_http_read_response(nng_http *conn, nng_aio *aio); +``` + +The {{i:`nng_http_read_response`}} function starts an asynchronous read from the +HTTP connection _conn_, reading an HTTP response into the response associated with _conn_, including all +of the related headers. + +It does _not_ transfer any response body. To do that, use [`nng_http_read_all`] or [`nng_http_read`]. + +> [!NOTE] +> At this time we have no API support for reading chunked transfers directly. Applications that +> need to do so may use the direct read functions. + +> [!TIP] +> An easier one-shot method for many use cases might be [`nng_http_transact`]. + +### Submitting the Transaction + +```c +int nng_http_transact(nng_http *conn, nng_aio *aio); +``` + +The HTTP request is issued, and the response processed, asynchronously by the {{i:`nng_http_transact`}} function. +When the function is complete, the _aio_ will be notified. + +The {{i:`nng_http_transact`}} function is used to perform a complete +HTTP exchange over the connection _conn_, sending the request +and attached body data to the remote server, and reading the response. + +The entire response is read, including any associated body, which can +subsequently be obtained using [`nng_http_get_data`]. + +This function is intended to make creation of client applications easier, +by performing multiple asynchronous operations required to complete an +entire HTTP transaction. + +If an error occurs, the caller should close _conn_ with [`nng_http_close`], as it may not +necessarily be usable with other transactions. + +> [!WARNING] +> If the remote server tries to send an extremely large buffer, +> then a corresponding allocation will be made, which can lead to denial +> of service attacks. +> Client applications should take care to use this only with reasonably +> trust-worthy servers. + +> [!NOTE] +> A given connection _conn_ should be used with only one +> operation or transaction at a time as HTTP/1.1 has no support for +> request interleaving. + +This function returns immediately, with no return value. +Completion of the operation is signaled via the _aio_, and the final result +may be obtained via [`nng_aio_result()`]. + +### Response Body + +## Server API + +### Handlers + +### Sending the Response + +```c +void nng_http_write_response(nng_http *conn, nng_aio *aio); +``` + +Normally the server will send any attached response, but there are circumstances where +a response must be sent manually, such as when [hijacking][`nng_http_hijack`] a connection. + +In such a case, {{i:`nng_http_write_response`}} can be called, which will send the response and any attached data, asynchronously +using the [`nng_aio`] _aio_. + +By default, for `HTTP/1.1` connections, the connection is kept open, and +will be reused to receive new requests. For `HTTP/1.0`, or if the client has requested +explicitly by setting the "Connection: close" header, the connection will be closed after the +response is fully sent. + +{{#include ../xref.md}} |