[#OSSL_HTTP_transfer]
= OSSL_HTTP_transfer
:mrdocs:

Open (or reuse), send one HTTP request, receive the response, and optionally keep the connection.

== Synopsis

Declared in `<openssl/http.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:BIO.adoc[BIO]*
OSSL_HTTP_transfer(
    xref:OSSL_HTTP_REQ_CTX.adoc[OSSL_HTTP_REQ_CTX]** prctx,
    char const* server,
    char const* port,
    char const* path,
    int use_ssl,
    char const* proxy,
    char const* no_proxy,
    xref:BIO.adoc[BIO]* bio,
    xref:BIO.adoc[BIO]* rbio,
    xref:OSSL_HTTP_bio_cb_t.adoc[OSSL_HTTP_bio_cb_t] bio_update_fn,
    void* arg,
    int buf_size,
    xref:stack_st_CONF_VALUE.adoc[stack_st_CONF_VALUE] const* headers,
    char const* content_type,
    xref:BIO.adoc[BIO]* req,
    char const* expected_content_type,
    int expect_asn1,
    size_t max_resp_len,
    int timeout,
    int keep_alive);
----

== Return Value

Response‐body BIO owned by the caller (free with BIO_free*), or NULL on failure.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *prctx*
| Optional address of an OSSL_HTTP_REQ_CTX*; reuses *`prctx` when non‐NULL, else opens; may be set to NULL when closed.
| *server*
| Hostname or address to contact when opening a new connection.
| *port*
| Service port, or NULL for the default (80/443).
| *path*
| Request path (or absolute URI for a proxy).
| *use_ssl*
| Nonzero to use HTTPS (requires `bio_update_fn` when opening via sockets).
| *proxy*
| Optional HTTP(S) proxy, or NULL to consult environment defaults.
| *no_proxy*
| Optional comma/whitespace host exclusion list, or NULL for environment defaults.
| *bio*
| Optional write BIO; NULL builds an internal connect BIO from `server/port.`
| *rbio*
| Optional read BIO used with `bio` when both are non‐NULL (no auto‐connect).
| *bio_update_fn*
| Optional connect/disconnect BIO callback (required for TLS when `bio` is NULL).
| *arg*
| Callback argument for `bio_update_fn` (not consumed).
| *buf_size*
| Max header line length / read chunk; <= 0 uses the default.
| *headers*
| Optional additional request headers, or NULL.
| *content_type*
| Content‐Type for `req,` or NULL.
| *req*
| Optional request‐body BIO, or NULL for a GET‐style exchange.
| *expected_content_type*
| Expected response Content‐Type, or NULL.
| *expect_asn1*
| Nonzero if the response body should be treated as ASN.1 DER.
| *max_resp_len*
| Maximum accepted response length in bytes.
| *timeout*
| Soft overall timeout in seconds for this exchange.
| *keep_alive*
| Keep‐alive preference (0/1/2 as for OSSL_HTTP_set1_request()).
|===


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