Is proxy to proxy is possible without Exchange Infrastructer (XI)

Question

Is proxy to proxy is possible without Exchange Infrastructer (XI)?
my question is if both applications can generate xml, do they require xi to exchange messages or it can connect directly.
how do they communicate? Is the correct?

Answer 1

Proxy and interface generation can be used in two ways:
- XI runtime and communication by Integration Server
- Web Service Runtime
Currently, Web Service Runtime can only be used for synchronous communication. You can define a web service and make a point to point connection without using the Integration Server.
I'm pasting a help document on this:
Point-to-Point Connections
If two communicating ABAP proxies don't require any of the services that are provided by the Integration Server, you can use the logical port to switch to the Web service runtime and thereby accelerate the rate of message exchange. In addition to the logical port, you also require a virtual interface and a Web service, which has been released in transaction WSADMIN for the generated server proxy. To address the receiver at the logical port, create an HTTP destination to the released Web service and enter the destination in the logical port.
The only other difference between the programming models is the protocols that are available. Because the XI Runtime supports Exactly Once In Order quality of service, there is an asynchronous protocol available that enables you to set the serialization context. You access the protocol the same way in both cases: Using the GET_PROTOCOL method of the proxy, you get a protocol instance that provides the required attributes and methods for the protocol. If the active runtime does not support the protocol, an exception is triggered.
As illustrated above, you can switch from XI communication using ABAP proxies to communication using Web services. However, the reverse is not possible because message interfaces support only a subset of the range of WSDL commands. For example, the XI protocol expects a predefined structure for fault messages whereas a fault message can have any structure in WSDL.
In addition to a point-to-point connection using the Web service runtime or a connection using the XI Runtime, there is also a third option. Since the Integration Server can process SOAP messages, you can also call a Web service by using the Integration Server. The Integration Server receives the SOAP message from the caller and forwards it to a receiver in accordance with the configuration in the Integration Directory (here, too, only synchronous calls are currently possible). Therefore, the receiver does not have to be a proxy. Because you can use the services of the Integration Server for this Web service call, it is known as an enhanced Web service. The following steps are required to define an enhanced Web service:
1. To be able to generate a WSDL description for the caller, you require a message interface. This can be either an outbound or inbound message interface. The message interface is not necessarily required for further configuration because it describes only the signature for the caller.
2. In the Integration Builder for configuration, call the menu Tools -> Define Web Service. You create a WSDL description by entering the following details in the wizard:
• The address of the Integration Server or another Web server that is to receive the SOAP call
• The message interface from the first step to publics the call signature via the WSDL document
• Details about the sender of the SOAP message (party, service and outbound interface)
• When the Integration Server receives the SOAP message, it requires these details to evaluate the configuration data. You enter the details about the sender in logical routing or interface mapping and in the colaboration agreements.
3. The caller can use the generated WSDL description to generate a client proxy and then send the SOAP message to the Integration Server by using the Web service runtime. You configure the receiver for the SOAP message on the Integration Server.
Hope this helps.
Regards,
Gökhan