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Figure 10: VidClient main window

4.4 Infra-red Tunnelling Application

The Visual C++ frameworks for the VidClient and VidServer applications were duplicated and used

as a basis for the infra-red tunnelling client and server. They were renamed IRClient and IRServer.

The duplicated frameworks were modiﬁed so that IRClient reads data from the serial port, buﬀers

it, and sends it to IRServer. IRServer in turn sends it to the other client.

The infra-red tunnelling application could be used for other purposes. Any byte-based serial device

that can withstand a certain amount of latency can be substituted for the infra-red transceivers.

Such devices may include printers and some storage devices.

The serial device needs to be byte-based in order for it to work correctly. This means that it

sends or receives data in packets of bytes, not bits. When application software reads from the serial

port, the data received is a multiple of bytes. If a non-byte-based device sends one bit of data to a

PC’s serial port, the computer pads the data with zeros to ﬁll one byte (IRDA 2000). It is up to

the application to do any required data conversion.

Since neither IRClient nor IRServer do IrDA data translation, the data that IRClient sends may

not be what is received if a non-byte-based serial device is used. If data translation were added, this

would limit the use of the application, since it would now only work with a particular serial device.

However, most devices are byte-based, since they are intended to be used directly with PCs.

The IRClient and IRServer applications are similar in design to their VidClient and VidServer

counterparts. IRServer waits for incoming connections on port 2200 by default, so that it doesn’t

clash with VidServer’s waiting port.

IRClient, like VidClient, initially displays a dialog asking the user to enter the host name of the

IRServer they wish to connect to (VidClient’s identical dialog box is shown in Figure 9). IRClient

then connects to IRServer’s listening port, and displays a window containing a list of timestamped

events (see Figure 12). Events displayed mainly involve server connection and disconnection and any

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