PhoneNet is an asynchronous terminal line-based transport designed for use with PMDF, MMDF, and CSNET. When it operates in master mode, PhoneNet is capable of "dialing out" over telephone lines to establish a connection with a PhoneNet slave on another machine. When it operates in slave mode, PhoneNet responds to a remote master's requests for message transfers.

PhoneNet is divided into two separate protocols. The lower "link-level" protocol, called the "dial protocol", provides a basic byte-stream environment. It is responsible for connection acquisition and management, character set translation and flow control. Dial is only used on asynchronous terminal lines.

The higher-level protocol, called the "phone protocol", is responsible for the semantics of mail transfer. It must establish the context and then pass individual messages. The overall structure of PhoneNet and the interaction of these two protocols is shown in Figure 24-1.

Figure 24-1 The Structure of PhoneNet

The following sections describe many, but not all, aspects of PhoneNet. In particular, the various input and output files used by PhoneNet channels are described in detail. However, the internal format of the dial and phone protocols are not described here. Refer to the files phone.ovr and dialproto.col in PMDF's documentation directory, (PMDF_DOC: on OpenVMS, or /pmdf/doc/ on UNIX, or usually C:\pmdf\doc\ on NT), for information on, respectively, the phone and dial protocols.

Four steps are required to set up a PhoneNet channel: (1) Add the channel to your PMDF configuration, (2) Create an option file for the channel, (3) Create a phone_list.dat file listing your serial devices, and (4) Create a script file that provides the necessary modem commands and login sequences. Each of these steps is described in detail in the following sections.

PhoneNet channels are not generated by the automatic configuration generator.