Integrating Business Systems by Using ABAP Proxies 
The following documentation describes an integration scenario in which the business system, which is connected to the Integration Server by means of ABAP proxies, takes on the role of either a sender system or a receiver system, or both.
Use
SAP systems based on AS 6.40 or higher can execute data exchange using messages and HTTP. These systems can use ABAP proxies to connect to the Integration Server.
Note
SAP systems up to and including Release 4.6 are not able to exchange data by using XML messages and HTTP. Such systems can only connect to the Integration Server by means of the IDoc adapter or the RFC adapter.
To connect the platform-independent service interfaces, which are stored in the Enterprise Services Repository, to the Integration Server, use the ABAP proxy interface.
Description
You can use executable ABAP proxies to exchange messages between a business system and the Integration Server. Executable ABAP proxies are shipped by SAP with all platform-independent service interfaces. However, you have to generate these proxies first before you can use them for your own interfaces.
An application in a business system calls a client proxy to send a message. The proxy runtime receives the message and the Integration Server processes it.
To forward messages to a receiver business system, the proxy runtime receives the message on the receiver system, and then calls the ABAP class that implements the relevant server proxy.
Connection Using ABAP Proxy
The local Integration Engine has the task of a message sender or receiver here. It does not perform any mapping or routing actions.
Example
A SAP AS 6.40 system uses a client proxy to send a message to the Integration Engine. The message is processed by the Integration Server. This determines two receivers:
Another Web AS 6.40 System
A system that cannot receive XML messages directly (for example, an SAP 4.0B system)
On the receiver side, the system based on SAP AS 6.40 receives a message. The message is used by a server proxy to call the ABAP class. The connection of the other receiver system takes place using the IDoc or RFC adapter.