= nng_http_conn_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_conn_transact - perform one HTTP transaction on connection

== SYNOPSIS

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

void nng_http_conn_transact(nng_http_conn *conn, nng_http_req *req,
    nng_http_res *res, nng_aio *aio);
----

== DESCRIPTION

The `nng_http_conn_transact()` function is used to perform a complete
HTTP exchange over the connection _conn_, sending the request _req_
(and attached body data) to the remote server, and reading the response
_res_.
The entire response is read, including any associated body, which can
subsequently be obtained using
`<<nng_http_res_get_data.3http#,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.

If an error occurs, the caller should close _conn_ with
`<<nng_http_conn_close.3http#,nng_http_conn_close()>>`, as it may not
necessarily be usable with other transactions.

A similar function,
`<<nng_http_client_transact.3http#,nng_http_client_transact()>>`,
exists.
That function behaves similarily, but creates a connection on demand
for the transaction, and disposes of it when finished.

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.

WARNING: 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.3#,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.
`NNG_EPROTO`:: An HTTP protocol error occurred.
`NNG_ETIMEDOUT`:: Timeout waiting for data from the connection.

== SEE ALSO

[.text-left]
<<nng_aio_alloc.3#,nng_aio_alloc(3)>>,
<<nng_aio_result.3#,nng_aio_result(3)>>,
<<nng_strerror.3#,nng_strerror(3)>>,
<<nng_http_client_connect.3http#,nng_http_client_connect(3http)>>,
<<nng_http_client_transact.3http#,nng_http_client_transact(3http)>>,
<<nng_http_conn_read_res.3http#,nng_http_conn_read_res(3http)>>,
<<nng_http_conn_read_all.3http#,nng_http_conn_read_all(3http)>>,
<<nng_http_conn_write_req.3http#,nng_http_conn_write_req(3http)>>,
<<nng_http_res_get_data.3http#,nng_http_res_get_data(3http)>>,
<<nng.7#,nng(7)>>
