FB_IotHttpClient

This function block enables communication with a HTTP server.

A client function block is responsible for the connection to exactly one server. The Execute() method of the function block must be called cyclically to enable the functionality of the HTTP client. The exact resource on the server is specified with the sUri property of the function block FB_IotHttpRequest.

All connection parameters exist as input parameters and are evaluated when a connection is established.

Syntax

Definition:

FUNCTION BLOCK FB_IotHttpClient 
VAR_INPUT
    //default is local host
    sHostName          : STRING((ParameterList.cSizeOfHttpClientHostName-1)) :=’127.0.0.1’;
    //default is 80
    nHostPort          : UINT :=80;
    bKeepAlive         : BOOL :=TRUE;        
    tConnectionTimeout : TIME :=T#10s;
    //optional parameter
    stTLS              : ST_IotSocketTls;
END_VAR
VAR_OUTPUT
    bError             : BOOL;
    hrErrorCode        : HRESULT;
    bConfigured        : BOOL;
    //TRUE if connection to server is established
    bConnected         : BOOL;
END_VAR

Inputs

Name	Type	Description
sHostName	STRING (255)	sHostName can be specified as a name or as an IP address. If no information is provided, the local host is used.
nHostPort	UINT	The host port can be specified here. The default value is 80 mm.
bKeepAlive	BOOL	Specifies whether the connection to the server should be maintained until either the server or client terminates it. Please note that not every server supports this function.
tConnectionTimeout	TIME	Specifies the connection timeout.
stTLS	ST_IotSocketTls	If the server offers a TLS-secured connection, the required configuration can be implemented here.

Outputs

Name	Type	Description
bError	BOOL	Becomes TRUE when an error situation occurs.
hrErrorCode	HRESULT	Returns an ADS return code. An explanation of the possible ADS return codes can be found in the Appendix.
bConfigured	BOOL	Becomes TRUE when the initial configuration is complete.
bConnected	BOOL	Becomes TRUE if a connection to the host is established. Please note that the connection is usually closed after each request, depending on the input parameter bKeepAlive.

Methods

Name	Description
Disconnect	Disconnects the client from the server if there is an active connection.
Execute	Method for background communication with the TwinCAT driver. The method must be called cyclically for every function block instance. If the method is called for the first time before the parameters are changed, default values are used. In this case, the parameters can only be changed by Re-parameterization.

Name

Description

Disconnect

Disconnects the client from the server if there is an active connection.

Execute

Method for background communication with the TwinCAT driver. The method must be called cyclically for every function block instance.

If the method is called for the first time before the parameters are changed, default values are used. In this case, the parameters can only be changed by Re-parameterization.

Requirements

Development environment	Target platform	PLC libraries to include
TwinCAT v3.1.4024.7 or higher	IPC or CX (x86, x64, ARM)	Tc3_IotBase