Bonjour Service Discovery Sample

Purpose

This sample demonstrates how to use ZeroConf service discovery mechanism for both publishing and discovering services on the network.

Prerequisites

Bonjour for Windows is required to run this sample. It can be downloaded free of charge from the Apple's website http://support.apple.com/downloads/Bonjour_for_Windows.

How it works

First, the service have to be made discoverable. To make a service discoverable it is necessary to do two things:

• Place and configure TROZeroConfRegistration component on the server's main form.
• Call SetZeroConfDetails procedure in the service implementation unit's initialization section.

The TROZeroConfBrowser component is used to discover available services on the network. Discovery process is performed in the background and corresponding events are being fired. When application is notified about new service available it have to start resolve procedure to obtain host name (address) and port number where to connect to. After hast name and port are obtained, the application can construct target URL and connect to the server as ususal.

Examine the code

• See the how the TROZeroConfRegistration component is configured on the server's main form.
• See how the SetZeroConfDetails procedure is being called in the service implementation unit. Notice how service type is specified there.
• See the how the TROZeroConfBrowser component is configured on the client side.
• Examine TClientForm.ROZeroConfBrowserServiceAdded and TClientForm.ROZeroConfBrowserServiceRemoved event handler to see how the client application responds to service availability change. Notice that these handlers are called in the thread other than GUI main. So special processing is required to interact with GUI components. In this sample main thread invokation is implemented usning custom windows messages. Message parameters lParam and wParam contain pointer to the procedure to be called and pointer to the procedure's parameter.
• Examine TClientForm.btUseServiceClick to see how TargetURL is constructed.

Getting started

• Build the sample.
• Start the server application. Server's responce string can be changed. Start the server with the 'Start server' button.
• Start the client application and see how server is discovered.
• Click 'Use service' button to communicate with the server.
• Try to run several servers on several machines or local host. See how services list changes when servers are being started and stopped. Select discovered services from the list and invoke different remote services.