Progress
External Program
Interfaces
Reasons To Use Sockets
Sockets allow your 4GL application to interact with other applications built using any language and deployed on any network machine using a standard communications model. 4GL sockets are integrated with the 4GL event model so you can use a single mechanism to handle user-interface events, AppServer asynchronous request completion events, and socket events. Applications that lend themselves to socket communications with the 4GL include:
Alternative 4GL mechanisms that allow socket access include the Host Language Call Interface (HLC) and shared library access described in this manual. However, 4GL sockets provide a native 4GL mechanism that is much easier to program and that is well-integrated with the 4GL event model.
The Progress implementation provides low-level access to TCP/IP sockets. In the 4GL, a socket client and server each send and receive data as a stream of bytes, accessed as a MEMPTR data type. The formatting of this data stream is entirely application dependent. You can marshal and unmarshal data streams according to your application requirements using the 4GL statements and functions available to manipulate MEMPTR data (see the "Using MEMPTR To Reference External Data" section).
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