Communications Tools

Today, the term ‘communications’ usually refers to links created between computers by means of high-level protocols, such as Internetworking Protocol (IP), which forms the basis of the Internet. Although modern versions of the Mac OS also support such mechanisms, they also include software that provides communication at a much lower level, allowing information to be conveyed directly between computers, either by means of a serial port or a modem and a telephone line.

Normally, a communications application is required for such a data transfer, although some general-purpose Mac OS programs, such as ClarisWorks 5, can also be used. A typical application has a Settings menu that leads you into the following kinds of dialogue:-

Dialogue ​NameFunction
ConnectionData Link Layer:
Ensures ​hardware ​can ​convey ​data ​bits
TerminalTerminal Emulation:
Makes ​the ​Mac ​act ​as ​another ​type ​of ​machine
File ​TransferTransport Layer:
Conveys ​files ​reliably ​over ​a ​link

The content of such dialogues is often provided by the Communications Toolbox (CTB), part of the Mac’s system software. The CTB uses communications tools, also known as basic connectivity tools, which are stored as individual files in the Extensions folder. These tools work with any suitable hardware, including a CTB-compatible serial port expansion card.

The following sections describe how to use an application that’s based on the CTB windows. The screen shots are from ClarisWorks 5, an application that uses the CTB throughout.

Connection Settings

These settings match the software to the actual hardware used to create a link, informing the computer about the port that’s in use and what’s connected to it.

Depending on your version of the Mac OS, there can be restrictions on how you can use the Printer or Modem ports for other purposes whilst AppleTalk is active. For example, with Classic AppleTalk in operation the Printer port can’t be used for anything other than conveying LocalTalk data.

With the Open Transport version of AppleTalk you can use whichever port isn’t assigned to AppleTalk. However, if you need both the Printer and Modem ports for serial devices, you must ensure that the Remote Only extension is available and selected in the AppleTalk control panel.

The following connection tools are commonly used:-

Apple Modem Tool

This tool is suitable for almost any modem and a telephone link, although it can be difficult to set up if you employ a non-standard modem or require to use some of its more advanced features.

The window is shown here:-

Providing you select the correct device under the Modem menu, most of the default settings should give reasonable results. Note, however, that the Port Settings area is particularly crucial.

The window’s settings are as follows:-

When dialling

Dial Phone Number: number for which the settings apply

Dialling Method: select Touch-Tone, Pulse or Mixed, as required by your phone system

Redial: number of attempts the modem should make to get a connection

When Answering

Answer phone after: the number of times the phone rings before the modem responds

Modem options

Modem: select your modem from the list, or choose Hayes-Compatible if not shown

Error Correction: select Required, Optional or None (greyed-out if unavailable)

Correction Type: select Software MNP or Hardware (greyed-out if unavailable)

Display Modem Monitor Window: select only if required

Port Settings

Baud Rate: select a suitable rate (only rates for your modem are shown)

Parity: select None, Even or Odd (usually None)

Data Bits: the number of bits in a byte, such as 5,6,7 or 8 (usually 8)

Stop Bits: number of bits indicating end of a byte, such as 1, 1.5 or 2 (usually 1)

Handshake: select None, XON/XOFF, DTR & CTS, DTR Only, CTS Only

Cabling: click on this button to see a picture of the modem to computer cable

Port: select Modem, Printer or expansion card port, as shown by icons

If you have an unusual telephone circuit or non-standard modem you should select Custom Modem in the Modem pop-up menu, which causes this window to appear:-

This contains the following:-

Modem Command Strings

Initialization: sets up modem options at beginning of a session; see modem manual for details

Ring Response: see your manual for details

Disable modem MNP: lets communication application disable MNP hardware in the modem

MNP Confirmation: message from application to modem, confirming the use of MNP

Modem auto-buffers connect speeds: select if modem has buffers for different speeds

Modem supports software error correction: select if modem supports MNP or V.42 software

Modem supports hardware error correction: select if modem contains MNP or V.42 hardware

If you check the error correction boxes in the above, the Error Correction and Correction Type pop-up menus in the Menu options area of the main window cease to be greyed-out. However, this only happens when the appropriate type of modem is selected in the Modem menu.

Serial Tool

This tool should be used if you want to sent data directly to another computer, terminal or personal organiser. It’s ideal for transferring data between a Mac OS machine and a PC.

Its simple window contains the following options:-

Port Settings

Baud Rate: set to 75, 110, 134.5, 150, 200, 300, 450, 600, 1200, 1800, 2000, 2400, 3600, 4800, 9600, 19200, 38400 or 57600 bit/s, so as to match the other device

Parity: select None, Even or Odd (usually None)

Data Bits: the number of bits in a byte, such as 5,6,7 or 8 (usually 8)

Stop Bits: number of bits indicating end of a byte, such as 1, 1.5 or 2 (usually 1)

Handshake: select None, XON/XOFF, DTR & CTS, DTR Only, CTS Only

Current Port

Select Modem, Printer or expansion card port, as shown by icons

When Closing Document

Hold Connection: retains connection when closing application’s communication document

Remind to Disconnect: gives reminder when closing document

Terminal Settings

Traditionally, mainframe computers are reached via a dumb terminal, consisting of a screen, keyboard and serial port. Using the correct terminal settings, you can emulate such a terminal.

The following terminal tools are commonly used:-

TTY Tool

This emulates a simple teletype (TTY) link, also known as Telex, which is normally employed for conveying 7-bit data to a teleprinter.

Here’s the window provided by this tool:-

which has the following settings:-

On Line: when selected any data you type is sent down the link

Local Echo: what you type appears on the screen

Width: the size of text in a connection window, either 80 or 132 columns of characters

Size: the font size of text in the window, usually 9 point or 12 point

Characters

Show Control Characters: select to see normally invisible characters

Auto Wrap to Next Line: saves you pressing Return at the end of each line

Holding Down Keys Will

Auto Repeat Keys: when a key is held down a string of characters is produced

Repeat Control Keys: as above, but for control commands

Text Cursor

Block: selected text is shown as white text in a black block

Underline: selected text is underlined

Scroll Text

Jump: scrolling causes text to move to next block

Smooth: scrolling operates normally

Swap ‘Backspace’ & ‘Delete’: swaps the keys for anyone not used to a Mac keyboard

New Line on a Return: moves to new line on pressing Return or when receiving LF (line feed)

VT102 Tool

This emulates a simple computer terminal of the VT52, VT100 or VT102 type, as used for conveying 7-bit data. The VT100 and VT102 systems are compatible, although the ANSI variation uses separate alphanumeric keys and cursor keys whilst the DEC variant employs escape sequences for the alphanumeric characters plus an alternative set of cursor codes.

The tool uses the four windows described below, which are selected by the scrolling icon list on the left of the main window.

General Window

Terminal: select ANSI/VT102 or VT52, as required

On Line: select to send anything that you type down the link

Local Echo: select to see what you type appear on the screen

Text Cursor

Block: selected text is shown as white text in a black block

Underline: selected text is underlined

Show Status Bar: provides bar at top of VT102 window, simulating VT102 keyboard indicators

Show Tab Ruler: puts a ruler at top of the VT102 window

Answerback Message: for identifying your Mac with a remote computer

Screen Window

Width: the size of text in a connection window, either 80 or 132 Columns of characters

Size: font size for text in the window, usually 9 point or 12 point

Characters

Show Control Characters: lets you see characters that are normally invisible

Auto Wrap to Next Line: saves pressing Return at the end of each line

Insert Characters: lets you type over existing characters

Origin at Scrolling Margin: for moving cursor outside the scrolling region

Scroll Text

Jump: scrolling causes text to move to next block

Smooth: scrolling operates normally

Inverse Video: produces white text on black background, as used in terminals

Keyboard Window

Numeric Keypad Generates

Numeric Sequences: uses number keys, as in an ANSI terminal

Application Sequences: uses escape sequences, as in a DEC terminal

Cursor Keys Generate

ANSI Cursor Sequences: uses arrow keys, as in an ANSI terminal

Application Sequences: uses cursor codes, as in a DEC terminal

Swap ‘Backspace’ & ‘Delete’: swaps the keys for anyone not used to a Mac keyboard

Holding Down Keys Will

Auto Repeat Keys: when a key is held down a string of characters is produced

Repeat Control Keys: as above, but for control commands

Keyclick Sound: produces click when you press a key

New Line on a Return: moves to new line on pressing Return or when receiving LF (line feed)

Character Set Window

National Replacement: the main character set in use

You can switch between the Active Character Sets (GO and G1) and the Temporary Character Sets (G2 and G3) by pressing Ctrl-O and Ctrl-N while using the terminal. Each set can contain the National Replacement Set, a Graphics set or the International character Set.

File Transfer Settings

File transfer software should transport a file over a link without damage and at the highest possible speed. It’s vitally important that the same settings are used at both ends of the link.

The following file transfer tools are used:-

Text Tool

A very simple mechanism for transferring a plain text file over a link. Note that any resources in a text file, such as the styl (styled text) resource in a SimpleText document, are lost during transfer.

Timing

Delay per Character: delay accommodating slow systems, usually between 0 and 32767

Delay per Line: as above, but only introduced at the end of lines

Line Endings

End Lines With: use CR for Mac text, LF for Unix and CR & LF for a PC

Wrap Lines at Column: sets the display width, typically 80

XMODEM Tool

A standard protocol for transferring files over telephone lines using 8 data bits and no software handshaking. It employs CRC or checksums in blocks of 128 or 1024 bytes.

The tool‘s single window has settings for:-

Method

Select one of the following:-

MacBinary: for sending any Mac file, including its resource fork

MacTerminal 1.1: for sending any Mac file, assuming automatic file reception

Straight XMODEM: for sending a text file’s data fork, without converting line endings

XMODEM Text: for sending a text file’s data fork, with line ending conversion

Timing Options

Timeout After_Seconds: time that Mac waits for block of data before giving up transfer

Retry Up To_Times: number of times computer tries to send a block of data

Transfer Options

Select one of the following error correction systems:-

Standard: 128-byte data blocks with checksums

CRC-16: 128-byte blocks with CRC-16 correction

1K Blocks: 1024-byte blocks with CRC-16 checking, giving faster transfer

CleanLink: 1024-byte blocks with CRC-16 checking, no acknowledgement

Received Files Options

Creator ID: sets the Mac OS creator code for received files

Select: lets you set the creator code by choosing an application

Use Filename sent by Remote Computer: lets files keep their names

Enable Auto Receive: for automatically receiving files from a computer supporting this feature

Claris Kermit Tool

This is an alternative to XMODEM that uses its own transfer process. It’s supplied with ClarisWorks 5, requiring 8 data bits and no software handshaking.

The tool‘s single window has settings for:-

Transfer Options

Select one of the following systems:-

Standard Packet: 10-94 bytes long (usually 80)

Long Packet: 10-9024 bytes long (usually 1024)

Sliding Windows: for sliding windows protocol, using 2-31 bytes (usually 8)

Extra Long Packets: 10-857374 bytes long (usually 18050)

Kermit Options

Auto Receive: when a mark character is received the file transfer is started

Overwrite Existing Files: select to let an incoming file overwrite a file of the same name

Use Timeout_ seconds: time that Mac waits for block of data before giving up transfer

Retries: number of times computer tries to send a block

Method

Select one of the following:-

MacBinary: for any Mac file, including its resource fork

Binary: for sending a text file’s data fork only, without converting line endings

Text: for sending a text file’s data fork only, with line ending conversion

Received Files Options

Creator ID: sets the Mac OS creator code for received files

Select: lets you set the creator code by choosing an application

Other Transfer Tools

Other methods of transfer, some of which require special software, include XMODEM-1K, which gives a faster transfer since it always uses 1024-byte blocks. The more advanced ZMODEM provides a wide range of options including 16-bit or 32-bit CRCs. It can send files in batches and can resume the transfer should a crash occur in the middle of the process.

YMODEM, also known as YMODEM-Batch since it allows files to be sent in batches, is a variation of XMODEM that sends information about a file in its first block, including its file name, size and modification date. YMODEM-128, with 128-byte blocks, is rarely used, although the aforementioned YMODEM-1K is sometimes encountered. YMODEM-G is a further development of YMODEM, in which ACK signals are not used and instead reliance is placed on the error correction built into the modem. This makes it particularly suitable for direct connections between computers.

Communicating via a Modem

Most people use a modem to gain access to the Internet. This requires you to dial up an Internet service provider (ISP), giving you access to several different servers, each supporting the protocol required for a specific service, such as the World Wide Web (WWW), email or news.

Peer-to-Peer Communication

There are other uses for a modem, apart from the Internet. The simplest is peer-to-peer communication, where you dial up another modem and convey data directly between two machines. This is supported by the CTB tools described above, although it’s a technical process. However, such a simple system avoids the need to pay for the services of an ISP. In addition, this kind of link is more secure and usually faster, since the information doesn’t have to pass through any other computers.

Online Services

Working with an online service is similar in some ways to peer-to-peer communication, except that you communicate with a special computer that lets you download information or upload other material. The original bulletin board service (BBS) providers operated in this way, requiring an application such as FirstClass BBS, although these have been superseded by Internet news groups.

America OnLine (AOL) and CompuServe, complete with their own e-mail services, originated as online providers, supplying textual material, although they have now migrated to the Internet. CompuServe could be reached using MacCIM, a Mac version of the CompuServe Information Manager (CIM), a front-end to the original and rather rudimentary user interface. Areas of interest to Mac users could be obtained using keywords, such as MACNEW, MACAPP and MACFUN.

Testing a Modem

Having set up a communications application, you should be ready to make a connection. Whatever you type or whatever text that you receive normally appears in the connection window of your application: you can usually adjust the size of font and font style to taste.

The link between modem and computer can be tested in this window by typing AT and Return. As you type each character the modem’s status lights should flash. And when you finally press Return an OK should appear in the application’s window.

You can test the dialling in this mode by typing ATDT followed by the phone number and Return. You should hear any conversation on the modem’s speaker (if it has one). When you’ve finished enter a ; (semi-colon) to take the modem off-line.

Establishing Communication

The following information applies to a the ClarisWorks 5 application. Assuming you have the correct Connection Setting, you can try to communicate with another modem. Before doing so, you may need to make entries in the Phone Book, which appears under the Session menu.To establish a link, you must choose Session ➡ Open Connection. As the application dials the number something similar to this appears on the screen:-

ATDT 888-3456

where 888-3456 is the number you’re dialling. After a while, you should hear the modems happily screaming at each other: just press Return and hopefully the noise will stop.

Once you’ve made a connection you may find you can’t see what you’re typing. If so, you should check the Local Echo box in the Connection Settings window. Conversely, if everything you type appears twice you should deselect it. Similarly, you should turn Local Echo off for peer-to-peer communication, although you should enable it when communicating with a BBS.

Transferring Files

Having established keyboard communication you may wish to send or receive an entire file. Many protocols and terminals can handle a binary file, containing all possible digital values, whilst other services, such as email, can only use an ASCII text file, containing values between 0 and 127.

To send a file in ClarisWorks 5, simply select Session ➡ Send File, although if you want to send several files you should select Session ➡ Send Batch. To receive a file you must choose Session ➡ Receive File, and then you must wait.

©Ray White 2004.