==== Bapihandler stops working, when "Gateway Security" is activated ====

with SAP- Profile parameter //gw/acl_mode = 1//

Actual security advisories from SAP tell the customer to do so which is a good idea because it really increases security.
With active gateway security all programs which want to register need to be declared in a kind of whitelist file.
== Solution 1: ==
Switch off gateway security by setting //gw/acl_mode to 0// in transaction RZ10 or RZ11 
== Solution 2: ==
Define both whitelist files "secinfo" and "reginfo" in the directory /usr/sap/<SID>/<INSTANCE>/data/ on the SAP System.
== Sample for reginfo, only two lines required ==
**#VERSION=2 \\
P TP=ICARO**
== Sample for secinfo, also only two lines required ==
**#VERSION=2 \\
P HOST=* USER=* TP=ICARO\\
**
in both cases TP=ICARO is exactly the Program-ID
as defined in bin\saprfc.ini

Definition and Activation of secinfo and reginfo can be done from inside SAP in transaction SMGW, no need to manually edit files in filesystem of SAP Server (Menu -> Goto -> Expert Functions -> External Security -> ..... )

Following some links for more information:\\

http://wiki.sdn.sap.com/wiki/display/Security/Gateway+security+settings+-+extra+information+regarding+SAP+note+1444282

SAP Note 1480644: Activation of  SAP Gateway Security \\
SAP Note 1305851: Overview about reg_info and sec_info \\

List of Parameters:\\
http://help.sap.com/saphelp_nw73/helpdata/en/48/ad76299eff35b7e10000000a42189d/content.htm

Explanation of Parameters:\\
http://help.sap.com/saphelp_nw73/helpdata/en/48/ad5b358bc96744e10000000a421937/content.htm