Command group Flag affected Reversible Execute on client Platform(s)
External commands YES NO NO All


HTTPOpen (hostname[,service|port,secure {Default kFalse},verify {Default kTrue}, useproxy {Default kTrue}]) Returns socket


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.

HTTPOpen is a client command that opens an HTTP connection to a Web server.

Hostname is a Character field containing the hostname or IP address of an HTTP server. For example: or

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 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.

If useproxy is kTrue (the default), and proxy server parameters have been set using HTTPSetProxyServer, HTTPOpen connects to the proxy server, setting up a secure tunnel if the proxy server does not have a secure URL, but the requested connection is secure. If kFalse, HTTPOpen connects directly to the specified host and port.

If HTTPOpen succeeds, socket receives a positive number which is the socket for the new connection to the server. Otherwise, socket receives a negative error code. Possible error codes are listed in the Web Command Error Codes Appendix.


; Connect to the server IP address iHostName on port iPort and send
; the message iMessage
Calculate iHostName as ''
Calculate iPort as 6000
Calculate lMessage as 'Hello remote application'
HTTPOpen (iHostName,iPort) Returns iSocket
If iSocket>0
  ; connected
  HTTPSend (iSocket,lMessage) Returns lCharCount
End If