HTTPGet

Syntax

HTTPGet (host,uri[,cgilist,hdrlist,service|port,secure {Default kFalse},verify {Default kTrue},map+ {Default kFalse}]) Returns socket

Description

Note: The flag is set according to whether Omnis was able to make a call to this external command.

This Web command is multi-threaded, allowing another thread to execute in the multi-threaded server while it runs. Note that the same socket cannot safely be used concurrently by more than one thread.

HTTPGet is a client command that submits a GET HTTP request to a Web server.

Host is a Character field containing the hostname or IP address of the Web server.

URI is a Character field containing the URI to GET from the Web Server. For example, "/default.html", or "/cgi-bin/mycgiscript"

CGIList is an optional parameter. It is an Omnis list with two character columns. The list contains the CGI arguments to be appended to the URI. There is one row for each CGI argument. For example

Note: Before the values are sent to the Web server, HTTPGet automatically performs any CGI encoding required to pass special characters in the arguments. There is no need to call the CGIEncode command.

HdrList is an optional parameter. It is an Omnis list with two character columns. The list contains additional headers to add to the headers of the HTTP GET request. Note that the header name excludes the ‘:’, which HTTPGet inserts automatically when it formats the header.

For example

Service|Port is an optional parameter that specifies the service name or port number of the server. If you specify a service name, the lookup for the port number occurs locally. If you omit this argument, it defaults to the port number specified in the host, or if none is present, it defaults to 80 or 443, the default port for HTTP or HTTPS respectively (depending on the value of Secure).

Secure is an optional Boolean parameter which indicates if a secure connection is required to the server. Pass kTrue for a secure connection, in which case the built-in security technology will be used, so on Windows ‘Secure Channel’ (Schannel) is used, on macOS ‘Secure Transport’ is used, and on Linux OpenSSL is used.

Verify is an optional Boolean parameter which is only significant when Secure is not kFalse. When Verify is kTrue, the command instructs the installed SSL library to verify the server's identity using its certificate; if the verification fails, then the connection will not be established. You can pass Verify as kFalse, to turn off this verification; in this case, the connection will still be encrypted, but there is a chance the server is an impostor. In order to perform the verification, the installed SSL library uses the Certificate Authority Certificates in the cacerts sub-folder of the secure folder in the Omnis folder. If you use your own Certificate Authority to self-sign certificates, you can place its certificate in the cacerts folder, and the installed SSL library will use it after you restart Omnis.

Map+ is an optional Boolean parameter which when true indicates that plus characters in CGI parameter names and values in the CGIList are to be URL encoded as hex.

Socket receives the result of the request. HTTPGet opens a connection to the Web server, and formats and sends an HTTP GET request to the server. If the command succeeds, it returns the socket number for the connection to the WEB server; otherwise, it returns an error number which is less than zero. After successfully issuing HTTPGet, you should call HTTPRead to read the response from the server; ALWAYS call HTTPClose to close the connection and free the socket. Possible error codes are listed in the Web Command Error Codes Appendix.

HTTPGet adds the following header fields by default:

Note: After calling HTTPGet, you can call HTTPSend to send your own content, before you read the response, provided that you include Content-type and Content-length headers in the HdrList.

Example

# Open a connection to the web server and read the server response
# into lBuffer 
Calculate iHostName as  '0.0.0.0'
Do  lCGIList.$define(lAttribute,lValue)
Do  lCGIList.$add('Name','John Smith')
Do  lCGIList.$add('Email','john.smith@smiths.com')
HTTPGet (iHostName,'/default',lCGIList) Returns iSocket
HTTPRead (iSocket,lBuffer) Returns lCharCount
HTTPClose (iSocket) Returns lStatus