= nng_http_client_transact(3http)
//
// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
// Copyright 2018 Capitar IT Group BV <info@capitar.com>
//
// This document is supplied under the terms of the MIT License, a
// copy of which should be located in the distribution where this
// file was obtained (LICENSE.txt).  A copy of the license may also be
// found online at https://opensource.org/licenses/MIT.
//

== NAME

nng_http_client_transact - perform one HTTP transaction

== SYNOPSIS

[source, c]
----
#include <nng/nng.h>
#include <nng/supplemental/http/http.h>

void nng_http_client_transact(nng_http_client *client, nng_http_req *req,
    nng_http_res *res, nng_aio *aio);
----

== DESCRIPTION

The `nng_http_client_transact()` function is used to perform a complete
HTTP exchange.
It creates a new connection using _client_, performs the transaction by
sending the request _req_
(and attached body data) to the remote server, then reading the response
_res_, and finally closes the connection that it created.
The entire response is read, including any associated body, which can
subsequently be obtained using
xref:nng_http_res_get_data.3http.adoc[`nng_http_res_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.

A similar function,
xref:nng_http_conn_transact.3http.adoc[`nng_http_conn_transact()`],
exists.
That function behaves similarily, but uses an existing connection, which
can be reused.

NOTE: This function does not support reading data sent using chunked
transfer encoding, and if the server attempts to do so, the underlying
connection will be closed and an `NNG_ENOTSUP` error will be returned.
This limitation is considered a bug, and a fix is planned for the future.

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.

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 xref:nng_aio_result.3.adoc[`nng_aio_result()`].
That result will either be zero or an error code.

== RETURN VALUES

None.

== ERRORS

[horizontal]
`NNG_ECANCELED`:: The operation was canceled.
`NNG_ECLOSED`:: The connection was closed.
`NNG_ECONNRESET`:: The peer closed the connection.
`NNG_ENOMEM`:: Insufficient free memory to perform the operation.
`NNG_ENOTSUP`:: HTTP operations are not supported, or peer sent chunked encoding.
`NNG_EPROTO`:: An HTTP protocol error occurred.
`NNG_ETIMEDOUT`:: Timeout waiting for data from the connection.

== SEE ALSO

[.text-left]
xref:nng_aio_alloc.3.adoc[nng_aio_alloc(3)],
xref:nng_aio_result.3.adoc[nng_aio_result(3)],
xref:nng_strerror.3.adoc[nng_strerror(3)],
xref:nng_http_client_connect.3http.adoc[nng_http_client_connect(3http)],
xref:nng_http_conn_transact.3http.adoc[nng_http_conn_transact(3http)],
xref:nng_http_res_get_data.3http.adoc[nng_http_res_get_data(3http)],
xref:nng.7.adoc[nng(7)]