HTTP Functions

HTTP Functions


The HTTP functions described in this section control the transmission and content of HTTP requests.
HttpAddRequestHeaders
HttpEndRequest
HttpOpenRequest
HttpQueryInfo
HttpSendRequest
HttpSendRequestEx

HttpAddRequestHeaders

BOOL HttpAddRequestHeaders(
    IN HINTERNET hHttpRequest,
    IN LPCSTR lpszHeaders,
    IN DWORD dwHeadersLength,
    IN DWORD dwModifiers
);

Adds one or more HTTP request headers to the HTTP request handle.

hHttpRequest
Open HTTP request handle returned by HttpOpenRequest.
lpszHeaders
Headers to append to the request. Each header must be terminated by a CR/LF (carriage return/line feed) pair.
dwHeadersLength
Length, in characters, of lpszHeaders. If this parameter is -1L, the function assumes that lpszHeaders is zero-terminated (ASCIIZ), and the length is computed.
dwModifiers
Values used to modify the semantics of this function. Can be a combination of the following values:
HTTP_ADDREQ_FLAG_ADD
Adds the header if it does not exist. Used with HTTP_ADDREQ_FLAG_REPLACE.
HTTP_ADDREQ_FLAG_ADD_IF_NEW
Adds the header only if it does not already exist; otherwise, an error is returned.
HTTP_ADDREQ_FLAG_COALESCE
Coalesces headers of the same name.
HTTP_ADDREQ_FLAG_COALESCE_WITH_COMMA
Coalesces headers of the same name. For example, adding "Accept: text/*" followed by "Accept: audio/*" with this flag results in the formation of the single header "Accept: text/*, audio/*". This causes the first header found to be coalesced. It is up to the calling application to ensure a cohesive scheme with respect to coalesced/separate headers.
HTTP_ADDREQ_FLAG_COALESCE_WITH_SEMICOLON
Coalesces headers of the same name using a semicolon.
HTTP_ADDREQ_FLAG_REPLACE
Replaces or removes a header. If the header value is empty and the header is found, it is removed. If not empty, the header value is replaced.

HttpAddRequestHeaders appends additional, free-format headers to the HTTP request handle and is intended for use by sophisticated clients that need detailed control over the exact request sent to the HTTP server.

Note that for basic HttpAddRequestHeaders, the application can pass in multiple headers in a single buffer. If the application is trying to remove or replace a header, only one header can be supplied in lpszHeaders.

See also HttpSendRequest

HttpEndRequest

HttpEndRequest(
    IN HINTERNET hRequest,
    OUT LPINTERNET_BUFFERS lpBuffersOut,
    IN DWORD dwFlags,
    IN DWORD dwContext
    );

Ends an HTTP request.

hRequest
HINTERNET handle returned by HttpOpenRequest and sent by HttpSendRequestEx.
lpBuffersOut
Address of an INTERNET_BUFFERS structure.
dwFlags
Can be one of the following values:
HSR_ASYNC Identical to WININET_API_FLAG_ASYNC.
HSR_SYNC Identical to WININET_API_FLAG_SYNC.
HSR_USE_CONTEXT Identical to WININET_API_FLAG_USE_CONTEXT.
HSR_INITIATE Iterative operation (completed by HttpEndRequest).
HSR_DOWNLOAD Download resource to file.
HSR_CHUNKED Send chunked data.
dwContext
Double-word variable that contains the context value to use in asynchronous operations.

HttpOpenRequest

HINTERNET HttpOpenRequest(
    IN HINTERNET hHttpSession,
    IN LPCSTR lpszVerb,
    IN LPCSTR lpszObjectName,
    IN LPCSTR lpszVersion,
    IN LPCSTR lpszReferer,
    IN LPCSTR FAR * lpszAcceptTypes,
    IN DWORD dwFlags,
    IN DWORD dwContext
);

Opens an HTTP request handle.

hHttpSession
Handle to an HTTP session returned by InternetConnect.
lpszVerb
Address of a string that contains the verb to use in the request. If this parameter is NULL, the function uses "GET" as the verb.
lpszObjectName
Address of a string that contains the name of the target object of the specified verb. This is generally a file name, an executable module, or a search specifier.
lpszVersion
Address of a string that contains the HTTP version. If this parameter is NULL, the function uses "HTTP/1.0" as the version.
lpszReferer
Address of a string that specifies the address (URL) of the document from which the URL in the request (lpszObjectName) was obtained. If this parameter is NULL, no "referrer" is specified.
lpszAcceptTypes
Address of a null-terminated array of LPCSTR pointers indicating content types accepted by the client. If this parameter is NULL, no types are accepted by the client. Servers interpret a lack of accept types to indicate that the client accepts only documents of type "text/*" (that is, only text documents, and not pictures or other binary files).
dwFlags
Internet flag values. Can be any of the following values:
INTERNET_FLAG_CACHE_IF_NET_FAIL
Return the resource from the cache if the network request for the resource fails due to an ERROR_INTERNET_CONNECTION_RESET or ERROR_INTERNET_CANNOT_CONNECT.
INTERNET_FLAG_DONT_CACHE
Does not add the returned entity to the cache. Identical to the preferred value, INTERNET_FLAG_NO_CACHE_WRITE.
INTERNET_FLAG_HYPERLINK
Forces a reload if there was no Expires time and no Last-Modified time returned from the server when determining whether to reload the item from the network.
INTERNET_FLAG_IGNORE_CERT_CN_INVALID
Disables Win32 Internet function checking of SSL/PCT-based certificates that are returned from the server against the host name given in the request. Win32 Internet functions use a simple check against certificates by comparing for matching host names and simple wildcarding rules.
INTERNET_FLAG_IGNORE_CERT_DATE_INVALID
Disables Win32 Internet function checking of SSL/PCT-based certificates for proper validity dates.
INTERNET_FLAG_IGNORE_REDIRECT_TO_HTTP
Disables the ability of the Win32 Internet functions to detect this special type of redirect. When this flag is used, Win32 Internet functions transparently allow redirects from HTTPS to HTTP URLs.
INTERNET_FLAG_IGNORE_REDIRECT_TO_HTTPS
Disables the ability of the Win32 Internet functions to detect this special type of redirect. When this flag is used, Win32 Internet functions transparently allow redirects from HTTP to HTTPS URLs.
INTERNET_FLAG_KEEP_CONNECTION
Uses keep-alive semantics, if available, for the connection. This flag is required for Microsoft Network (MSN), NT LAN Manager (NTLM), and other types of authentication.
INTERNET_FLAG_MAKE_PERSISTENT
No longer supported.
INTERNET_FLAG_MUST_CACHE_REQUEST
Causes a temporary file to be created if the file cannot be cached. Identical to the preferred value, INTERNET_FLAG_NEED_FILE.
INTERNET_FLAG_NEED_FILE
Causes a temporary file to be created if the file cannot be cached.
INTERNET_FLAG_NO_AUTH
Does not attempt authentication automatically.
INTERNET_FLAG_NO_AUTO_REDIRECT
Does not automatically handle redirection in HttpSendRequest.
INTERNET_FLAG_NO_CACHE_WRITE
Does not add the returned entity to the cache.
INTERNET_FLAG_NO_COOKIES
Does not automatically add cookie headers to requests, and does not automatically add returned cookies to the cookie database.
INTERNET_FLAG_NO_UI
Disables the cookie dialog box.
INTERNET_FLAG_PRAGMA_NOCACHE
Forces the request to be resolved by the origin server, even if a cached copy exists on the proxy.
INTERNET_FLAG_READ_PREFETCH
This flag is currently disabled.
INTERNET_FLAG_RELOAD
Forces a download of the requested file, object, or directory listing from the origin server, not from the cache.
INTERNET_FLAG_RESYNCHRONIZE
Reloads HTTP resources if the resource has been modified since the last time it was downloaded.
INTERNET_FLAG_SECURE
Uses SSL/PCT transaction semantics.
dwContext
Application-defined value that associates this operation with any application data.

HttpOpenRequest creates a new HTTP request handle and stores the specified parameters in that handle. An HTTP request handle holds a request to be sent to an HTTP server and contains all RFC822/MIME/HTTP headers to be sent as part of the request.

Use the InternetCloseHandle function to close the handle returned by HttpOpenRequest. InternetCloseHandle cancels all outstanding I/O on the handle.

The lpszReferer parameter to InternetOpen is used as the referrer for the HTTP request.

See also HttpAddRequestHeaders, HttpQueryInfo, InternetReadFile

HttpQueryInfo

BOOL HttpQueryInfo(
    IN HINTERNET hHttpRequest,
    IN DWORD dwInfoLevel,
    IN LPVOID lpvBuffer,
    IN LPDWORD lpdwBufferLength,
    IN OUT LPDWORD lpdwIndex,
);

Queries for information about an HTTP request.

hHttpRequest
Open HTTP request handle returned by HttpOpenRequest or InternetOpenUrl.
dwInfoLevel
Combination of the attribute to query and the flags that modify the request. The attributes can be any of the following values:
HTTP_QUERY_ACCEPT
Retrieves the acceptable media types for the response.
HTTP_QUERY_ACCEPT_CHARSET
Retrieves the acceptable character sets for the response.
HTTP_QUERY_ACCEPT_ENCODING
Retrieves the acceptable content-coding values for the response.
HTTP_QUERY_ACCEPT_LANGUAGE
Retrieves the acceptable natural languages for the response.
HTTP_QUERY_ACCEPT_RANGES
Retrieves the types of range requests that are accepted for a resource.
HTTP_QUERY_AGE
Retrieves the Age response-header field, which contains the sender's estimate of the amount of time since the response was generated at the origin server.
HTTP_QUERY_ALLOW
Receives the methods supported by the server.
HTTP_QUERY_AUTHORIZATION
Retrieves the authorization credentials used for a request.
HTTP_QUERY_CACHE_CONTROL
Retrieves the cache control directives.
HTTP_QUERY_CONNECTION
Retrieves any options that are specified for a particular connection and must not be communicated by proxies over further connections.
HTTP_QUERY_COOKIE
Retrieves any cookies associated with the request.
HTTP_QUERY_CONTENT_BASE
Retrieves the base URI for resolving relative URLs within the entity.
HTTP_QUERY_CONTENT_DESCRIPTION
Obsolete. Maintained for legacy application compatibility only.
HTTP_QUERY_CONTENT_DISPOSITION
Obsolete. Maintained for legacy application compatibility only.
HTTP_QUERY_CONTENT_ENCODING
Receives any additional content codings that have been applied to the entire resource.
HTTP_QUERY_CONTENT_ID
Receives the content identification.
HTTP_QUERY_CONTENT_LANGUAGE
Receives the language that the content is in.
HTTP_QUERY_CONTENT_LENGTH
Receives the size of the resource, in bytes.
HTTP_QUERY_CONTENT_LOCATION
Retrieves the resource location for the entity enclosed in the message.
HTTP_QUERY_CONTENT_MD5
Retrieves a MD5 digest of the entity-body for the purpose of providing an end-to-end message integrity check (MIC) for the entity-body. For more information, see RFC1864, The Content-MD5 Header Field, at http://ds.internic.net/rfc/rfc1864.txtExternal Link for more information.
HTTP_QUERY_CONTENT_RANGE
Retrieves the location in the full entity-body where the partial entity-body should be inserted and the total size of the full entity-body.
HTTP_QUERY_CONTENT_TRANSFER_ENCODING
Receives the additional content coding that has been applied to the resource.
HTTP_QUERY_CONTENT_TYPE
Receives the content type of the resource (such as text/html).
HTTP_QUERY_COST
No longer implemented.
HTTP_QUERY_DATE
Receives the date and time at which the message was originated.
HTTP_QUERY_DERIVED_FROM
No longer supported.
HTTP_QUERY_ETAG
Retrieves the entity tag for the associated entity.
HTTP_QUERY_EXPIRES
Receives the date and time after which the resource should be considered outdated.
HTTP_QUERY_FORWARDED
Obsolete. Maintained for legacy application compatibility only.
HTTP_QUERY_FROM
Retrieves the e-mail address for the human user who controls the requesting user agent if the From header is given.
HTTP_QUERY_HOST
Retrieves the Internet host and port number of the resource being requested.
HTTP_QUERY_IF_MATCH
Retrieves the contents of the If-Match request-header field.
HTTP_QUERY_IF_MODIFIED_SINCE
Retrieves the contents of the If-Modified-Since header.
HTTP_QUERY_IF_NONE_MATCH
Retrieves the contents of the If-None-Match request-header field.
HTTP_QUERY_IF_RANGE
Retrieves the contents of the If-Range request-header field. This header allows the client application to check if the entity related to a partial copy of the entity in the client application's cache has not been updated. If the entity has not been updated, send the parts that the client application is missing. If the entity has been updated, send the entire updated entity.
HTTP_QUERY_IF_UNMODIFIED_SINCE
Retrieves the contents of the If-Unmodified-Since request-header field.
HTTP_QUERY_LINK
Obsolete. Maintained for legacy application compatibility only.
HTTP_QUERY_LAST_MODIFIED
Receives the date and time at which the server believes the resource was last modified.
HTTP_QUERY_LOCATION
Retrieves the absolute URI used in a Location response-header.
HTTP_QUERY_MAX
Retrieves the maximum value of an HTTP_QUERY_* value.
HTTP_QUERY_MAX_FORWARDS
Retrieves the number of proxies or gateways that can forward the request to the next inbound server.
HTTP_QUERY_MESSAGE_ID
No longer implemented.
HTTP_QUERY_MIME_VERSION
Receives the version of the MIME protocol that was used to construct the message.
HTTP_QUERY_ORIG_URI
Obsolete. Maintained for legacy application compatibility only.
HTTP_QUERY_PRAGMA
Receives the implementation-specific directives that may apply to any recipient along the request/response chain.
HTTP_QUERY_PROXY_AUTHENTICATE
Retrieves the authentication scheme and realm returned by the proxy.
HTTP_QUERY_PROXY_AUTHORIZATION
Retrieves the header that is used to identify the user to a proxy that requires authentication.
HTTP_QUERY_PUBLIC
Receives methods available at this server.
HTTP_QUERY_RANGE
Retrieves the byte range of an entity.
HTTP_QUERY_RAW_HEADERS
Receives all the headers returned by the server. Each header is terminated by "\0". An additional "\0" terminates the list of headers.
HTTP_QUERY_RAW_HEADERS_CRLF
Receives all the headers returned by the server. Each header is separated by a carriage return/line feed (CR/LF) sequence.
HTTP_QUERY_REFERER
Receives the URI of the resource where the requested URI was obtained.
HTTP_QUERY_REFRESH
Obsolete. Maintained for legacy application compatibility only.
HTTP_QUERY_REQUEST_METHOD
Receives the verb that is being used in the request, typically GET or POST.
HTTP_QUERY_RETRY_AFTER
Retrieves the amount of time the service is expected to be unavailable.
HTTP_QUERY_SERVER
Retrieves information about the software used by the origin server to handle the request.
HTTP_QUERY_SET_COOKIE
Receives the value of the cookie set for the request.
HTTP_QUERY_STATUS_CODE
Receives the status code returned by the server. For a list of possible values, see HTTP Status Codes.
HTTP_QUERY_STATUS_TEXT
Receives any additional text returned by the server on the response line.
HTTP_QUERY_TITLE
Obsolete. Maintained for legacy application compatibility only.
HTTP_QUERY_TRANSFER_ENCODING
Retrieves the type of transformation that has been applied to the message body so it can be safely transferred between the sender and recipient.
HTTP_QUERY_UPGRADE
Retrieves the additional communication protocols that are supported by the server.
HTTP_QUERY_URI
Receives some or all of the Uniform Resource Identifiers (URIs) by which the Request-URI resource can be identified.
HTTP_QUERY_USER_AGENT
Retrieves information about the user agent that made the request.
HTTP_QUERY_VARY
Retrieves the header that indicates that the entity was selected from a number of available representations of the response using server-driven negotiation.
HTTP_QUERY_VERSION
Receives the last response code returned by the server.
HTTP_QUERY_VIA
Retrieves the intermediate protocols and recipients between the user agent and the server on requests, and between the origin server and the client on responses.
HTTP_QUERY_WARNING
Retrieves additional information about the status of a response that may not be reflected by the response status code.
HTTP_QUERY_WWW_AUTHENTICATE
Retrieves the authentication scheme and realm returned by the server.

The following modifiers can be used with the information values:

HTTP_QUERY_CUSTOM
Causes HttpQueryInfo to search for the header name specified in lpvBuffer and store the header information in lpvBuffer.
HTTP_QUERY_FLAG_COALESCE
Combines the values from headers with the same name into the output buffer.
HTTP_QUERY_FLAG_NUMBER
Returns the data as a 32-bit number for headers whose value is a number, such as the status code.
HTTP_QUERY_FLAG_REQUEST_HEADERS
Queries request headers only.
HTTP_QUERY_FLAG_SYSTEMTIME
Returns the header value as a standard Win32 SYSTEMTIME structure, which does not require the application to parse the data. Use for headers whose value is a date/time string, such as "Last-Modified-Time".
lpvBuffer
Address of the buffer that receives the information.
lpdwBufferLength
Address of a value that contains the length of the data buffer. When the function returns, this parameter contains the address of a value specifying the length of the information written to the buffer. When the function returns strings, the following rules apply:
  • If the function succeeds, lpdwBufferLength specifies the length of the string, in characters, minus 1 for the terminating null.
  • If the function fails and ERROR_INSUFFICIENT_BUFFER is returned, lpdwBufferLength specifies the number of bytes that the application must allocate to receive the string.
lpdwIndex
Address of a zero-based header index used to enumerate multiple headers with the same name. When calling the function, this parameter is the index of the specified header to return. When the function returns, this parameter is the index of the next header. If the next index cannot be found, ERROR_HTTP_HEADER_NOT_FOUND is returned.

HttpQueryInfo is used to return response or request headers from an HTTP request.

You can retrieve different types of data from HttpQueryInfo:

See also HttpOpenRequest

HttpSendRequest

BOOL HttpSendRequest(
    IN HINTERNET hHttpRequest,
    IN LPCSTR lpszHeaders,
    IN DWORD dwHeadersLength,
    IN LPVOID lpOptional,
    DWORD dwOptionalLength
);

Sends the specified request to the HTTP server.

hHttpRequest
Open HTTP request handle returned by HttpOpenRequest.
lpszHeaders
Additional headers to be appended to the request. This parameter can be NULL if there are no additional headers to append.
dwHeadersLength
Length, in characters, of the additional headers. If this parameter is -1L and lpszHeaders is not NULL, the function assumes that lpszHeaders is zero-terminated (ASCIIZ), and the length is calculated.
lpOptional
Address of any optional data to send immediately after the request headers. This parameter is generally used for POST and PUT operations. The optional data can be the resource or information being posted to the server. This parameter can be NULL if there is no optional data to send.
dwOptionalLength
Length, in bytes, of the optional data. This parameter can be zero if there is no optional data to send.

HttpSendRequest sends the specified request to the HTTP server and allows the client to specify additional headers to send along with the request.

The function also lets the client specify optional data to send to the HTTP server immediately following the request headers. This feature is generally used for "write" operations such as PUT and POST.

After the request is sent, the status code and response headers from the HTTP server are read. These headers are maintained internally and are available to client applications through the HttpQueryInfo function.

An application can use the same HTTP request handle in multiple calls to HttpSendRequest, but the application must read all data returned from the previous call before calling the function again.

See also InternetReadFile

HttpSendRequestEx

BOOL HttpSendRequestEx(
    IN HINTERNET hRequest,
    IN LPINTERNET_BUFFERS lpBuffersIn,
    OUT LPINTERNET_BUFFERS lpBuffersOut,
    IN DWORD dwFlags,
    IN DWORD dwContext
);

Sends the specified request to the HTTP server.

hRequest
HINTERNET handle returned by HttpOpenRequest.
lpBuffersIn
Optional. Address of an INTERNET_BUFFERS structure.
lpBuffersOut
Optional. Address of an INTERNET_BUFFERS structure.
dwFlags
Can be one of the following values:
HSR_ASYNC Identical to WININET_API_FLAG_ASYNC.
HSR_SYNC Identical to WININET_API_FLAG_SYNC.
HSR_USE_CONTEXT Identical to WININET_API_FLAG_USE_CONTEXT.
HSR_INITIATE Iterative operation (completed by HttpEndRequest).
HSR_DOWNLOAD Download resource to file.
HSR_CHUNKED Send chunked data.
dwContext
DWORD variable that contains the context value to use in asynchronous operations.

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