![[Terminal Window]](/file/23826/Macworld (1998-10).dmg/Serious Demos/MacComCenter™ 3.0/MCC 3.0 Retail Online Help/Media/MCC Terminal/TerminalMainView.gif)
An introduction to data communications was covered in Chapter 3. If you have not already read that chapter, we strongly suggest that you go back over the information contained therein.
The MacComCenter Plus Terminal application provides access to various data communications activities. When activated by double-clicking on the MCC Terminal icon, the Terminal Window will appear. The terminal display is located beneath the ModemMonitor / Terminal Status Bar. When you perform data activities, the data will appear in the terminal display as it is sent to or received from the modem. AT commands can be typed in directly and the modem responses can be read. For example, the Initialization String is comprised of AT commands. The modem response to the initialization string is the OK text, directly beneath it. To the right of the Terminal Window is a scroll bar, which allows you to review data that has scrolled up beyond the top of the Terminal Window.
The ModemMonitor runs along the top of the Terminal Window. The ModemMonitor is used in the same way status lights are used on an external modem. The ModemMonitor is a set of modem status lights on the Terminal Window. These status lights allow the user to be aware of the current modem status. There are 9 modem status lights visible in the ModemMonitor which indicate the following:
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FX: Fax Connection - The incoming or outgoing call is a fax. HS: High Speed - The established connection is at 9600 baud or higher. AA: Auto Answer - Flashes whenever a RING is detected by the modem. OH: Off Hook - The modem has picked up the telephone line. RX: Receive Data - The modem is receiving characters or data. TX: Transmit Data - The modem is transmitting characters or data. TR: Terminal Ready - The modem/computer is ready to send and receive commands. MR: Modem Ready - The modem is powered on. CS: Clear to Send - The modem is ready to receive more data. |
The Terminal Status Bar located to the right of the ModemMonitor provides you with a display of important communications settings and messages about current activities. For example, if you hang up following a modem call, the message DISCONNECTING... appears. Information in this message area also displays the current terminal emulation, the current line settings (baud rate, data bits, parity, stop bits), and the flow control being used.
Note: You can click on these line settings to quickly display the Modem Configuration dialog.
There are three ways to dial out of MacComCenter Plus to establish a data connection. For any number that you plan on calling repeatedly, adding the number to the Data Phonebook is the best choice. The second way to dial a number is via the MacComCenter Plus Dialer. The third way is to just type the Dial AT command to the modem.
The MacComCenter Plus Data Phonebook allows you to create a list of data numbers and settings to simplify dialing frequently called services.
To access the Phonebook, select MCC Phone List from the File menu. The Data Phonebook dialog box will appear.
To add a new number to the list, click on the New Entry button. To edit a previously entered number, highlight the desired entry and click on the Edit button. Either option will bring up the phone list edit dialog box.
Use the Name field to specify the name of the BBS or service for the entry. The Number field allows you to specify the phone number for the service.
The other fields deal with the more technical aspects of the connection. All of the option fields are pull down menus which show the available options for the selected field. While there is no set standard terminal type and line setting combination for every modem connection, there are some guidelines to follow which may be helpful.
To dial a number from the phone list, simply highlight the desired entry, and click on the Dial button. A short cut is to double click on the desired entry.
The majority of data communications sessions will begin with you dialing out to another modem, BBS or on-line service. The quickest way to perform this task is to simply dial the modem with the Dial command available under the Data menu. The Dialer dialog box will appear.
Simply enter the number by clicking on the desired numbers on the stylized phone pad, or type the numbers directly from your Macintosh keyboard. When the number has been entered, click on the Dial button. MacComCenter Plus will dial the number entered. The dialer will use the specified Baud Rate, Terminal, and Line Settings configured in the Modem Setup option under the Setup menu.
A file transfer is nothing more than copying a file from one computer to another. The modem connects the two computers together via the phone line, and a file transfer protocol is used to ensure that the file data is not corrupted during the transfer.
File transfers are divided into two basic types: Downloads and Uploads. When you download a file, you are copying a file from a remote computer to your local machine. When you upload a file, you are sending a file from your local machine to a remote computer. The steps necessary to perform a file transfer are outlined in Chapter 3. This chapter provides advanced information about the different file transfer protocols, and the advantages and disadvantages of each.
Some file transfer protocols can only handle a single file at a time. The ASCII, Xmodem (CRC) and Xmodem 1K protocols are examples of this type of protocol. When downloading, (copying a file from a remote computer to your local machine) you will need to enter a name for each file when using any of these protocols.
The Kermit, Ymodem, Ymodem-G, CompuServe B/B+, and Zmodem protocols let you transfer more than one file during the same transmission. They will also allow you to transfer a single file. When downloading, all of these protocols will receive the name of the file during the transfer, so it is impossible for files to be named incorrectly.
During a file transfer, the File Transfer Status dialog box will appear to keep you informed of the upload or download status. It will display the following information:
Protocol The file transfer protocol is displayed in the window title.
File name This is the name of the file currently being transferred.
File # This is the number of the current file being transferred in a batch. If you are sending a single file, the file number should be 1.
File size This item displays the size of the current file being transferred. Some protocols do not have the file size information on downloads. If this is the case, the file size would read <Unknown>.
Status The status of the file transfer contains the current action that MacComCenter Plus is performing during the file transfer.
Bytes sent/rcvd This field displays the number of bytes sent or received so far.
Block # This field displays which block of data is being transferred.
Block size This displays the size of each block being transferred. A block is the unit of data being transferred.
Retries This field displays how many retry attempts have occurred during the file transfer. These retransmissions are usually caused by line noise.
Time elapsed/left This displays how long the current transfer has lasted and how long until it's done.
Effective baud rate This displays the actual number of bits transferred per second.
Efficiency gauge The Efficiency gauge graphically displays the effective baud rate versus the connected baud rate. The higher the gauge reads, the better the efficiency.
Percent bar
The Percent bar graphically displays the percentage complete for the current file transfer.
This section describes the various protocols that MacComCenter Plus provides for transferring data files.
The ASCII protocol is a seven-bit protocol that consists of the 128 characters that make up the uppercase and lowercase alphabet, numbers, characters available on a standard keyboard, and certain special control characters.
There is no additional error checking characters sent during a transmission when using an ASCII transfer. ASCII is good for sending a burst transmission of raw text/data uninterrupted.
MacComCenter Plus implements the standard Kermit protocol. It was developed to meet the needs for file transfer between a number of different types of computers, including mainframes, mini computers and personal computers. Unlike Xmodem and Ymodem, Kermit uses variable packet sizes, with a maximum size of 1024 bytes. Like Ymodem, Kermit provides for batch file transfers.
In an effort to guard against undetected errors the original Xmodem was enhanced by replacing the 8 bit checksum with a 16 bit Cyclic Redundancy Check (CRC). This change provides a 99.9984% assurance of detecting any transmission errors. With the checksum method, it is possible for 1 out of 256 bad packets to have a valid checksum, and thus go undetected. With the CRC method only 1 out of 700 billion bad packets will generate a valid CRC. The CRC method also transmits 128 byte blocks or packets of data. If you select Xmodem CRC and the other system does not support it, MacComCenter Plus will automatically switch over to the standard Xmodem; to the user both methods appear to operate identically.
This method of Xmodem data transfer replaces the original 128 byte packets with packets of 1,024 bytes when possible. Assuming that no transmission errors are detected, this method of Xmodem data transfer will enlarge the packet size to 1K and maintain that packet size for as long as possible. Enlarging the packet size will improve the speed of the file transfer. If you attempt to receive a file using Xmodem 1K and the other side only supports Xmodem CRC, MacComCenter Plus will fall back to Xmodem CRC.
The Ymodem protocol (also called Ymodem Batch, Ymodem 1K, and Ymodem CRC) is very similar to Xmodem 1K, with two major differences -- with Ymodem you can automatically receive or send multiple files in one session, and file names are included with the transfer. In general, Ymodem is very fast, very safe and preferable to Xmodem, even for single files.
Ymodem-G is a file transfer protocol that provides the same error checking as Ymodem, but it will not perform any error recovery. Therefore, Ymodem-G requires an error-correcting modem or fax/modem with either MNP 2-4 and/or V.42. If both ends of the transmission meet the requirements, transfers can be exceptionally fast.
The Zmodem protocol is a popular protocol that lets you send multiple files in one transfer. Features include automatic downloading and the ability to send file names, sizes, and creation dates of each file. Also, if a data transmission is interrupted midway, Zmodem lets you resume the data transmission from the point where it left off.
The size of the data block varies with Zmodem, depending on the condition of the connection of the telephone line between the communicating devices. Moreover, both 32-bit and 16-bit CRC error-checking are available with Zmodem.
Zmodem is a relatively young transfer protocol, not identically implemented at all sites. If you are having problems with Zmodem transfers, you may wish to try Ymodem.
The CompuServe B/B+ protocol should be used when communicating with CompuServe.
The File Transfer Setup dialog allows you to set the file transfer attributes you want MacComCenter Plus to use. A number of check boxes are provided to turn options on or off. The File Transfer Setup dialog is available by selecting File Transfer from the Setup menu.
1/60 seconds between character This allows you to enter the number of seconds to wait before a character will be sent during a data communication session.
1/60 seconds between lines This allows you to enter the number of seconds to wait before a line will be sent during a data communication session.
Text file creator This allows you to enter the creator of a file to use as the default text editor. The file creator you choose will be the application that opens up the text file when you double-click on it from the Finder.
Add LF's on send This instructs MacComCenter Plus to add line feeds during the sending of a file during a data file transfer.
Strip LF's on receive This instructs MacComCenter Plus to remove line feeds during reception of a file during a data file transfer.
Default Send protocol This instructs MacComCenter Plus which protocol to use as a default when sending files. This will give you quick access to the most frequently used file transfer protocol for sending files. The command key equivalent for this is Cmd-U.
Default Receive protocol This instructs MacComCenter Plus which protocol to use as a default when receiving files. This will give you quick access to the most frequently used file transfer protocol for receiving files. The command key equivalent for this is Cmd-I.
This instructs MacComCenter Plus which MacBinary option to use during a data file transfer. The options are Smart MacBinary, Always MacBinary, and Never MacBinary. MacBinary should be used when downloading a Macintosh file. A Macintosh file consists of two forks, or parts. Using MacBinary when sending and receiving a file will put the two forks in their proper place. MacBinary files also contain file information.
Choosing Modem from the Setup menu causes the Modem Setup dialog to appear.
Initialization string The modem initialization string is the command set that MacComCenter Plus issues to the modem when the application is first started. The default string works with most modems and fax/modems. If your modem has special features or commands, the AT commands needed to enable them are entered here. Check your modem manual for a detailed breakdown of the AT command set.
Dial prefix The dial prefix is the command MacComCenter Plus issues to the modem when instructed to automatically dial a number. This entry will be used when dialing from a phone list, using the Dialer or connecting with CompuServe, Dow Jones or GEnie.
Dial suffix The dial suffix string, if defined, is added to the end of a number dialed with MacComCenter Plus. If this feature is used, you may need to begin the string with a comma to cause a delay before the suffix is transmitted. The dial suffix is useful when using some long distance services or calling cards.
Hang-up string The hang-up string is the command MacComCenter Plus issues to the modem when the Hang Up option is selected from the Data menu.
Redial attempts Allows you to specify how many times to redial a data number before canceling the data call.
Dial timeout The number of seconds MacComCenter Plus will wait before canceling the call.
Delay before redial Specifies the number of seconds to wait before attempting to redial a busy data number.
Answer on ring # Specifies how many rings MacComCenter Plus will wait to answer an incoming call.
Auto baud Tells MacComCenter Plus to automatically reset the baud rate if the modem makes a connection at a rate other than the rate specified at dialing.
Drop DTR on exit Specifies that DTR (Data Terminal Ready) will be toggled after exiting from a connection.
These options allow you to select the line speed, data format and flow control to be used during communications; these settings are independent of the settings in the data phone list. The Cancel button will exit without saving any changes. Press OK to remove the dialog and implement all option changes.
Baud rate Possible baud rate settings may vary from 300 to 57,600. Refer to your modem manual for the maximum baud rate that your modem will handle.
Data bits The allowable options are 5, 6, 7 or 8 data bits.
Parity Parity may be Odd, Even, or None. None only applies only when 8 data bits are selected.
Stop bits The allowable settings are 1, 1.5 or 2.
Flow control This option controls local flow control. Local flow control is the process of regulating the flow of data between the computer and the modem. This provides time to process the data received. Flow Control is usually not needed for 2400 bps data connections. XON/XOFF is a software flow control that involves the sending of special control codes as part of the data. RTS/CTS is hardware flow control that is implemented in both software and the modem hardware. Therefore your modem and cable must support the RTS/CTS standard for this method to be used. The RTS/CTS method is more reliable and is normally used with V.42 and MNP Level 5 and above modems.
Port Selection You may attach your modem to the Macintosh Modem port, Printer port or any other port supported by the Communications Toolbox. Select the port to which your fax/modem is connected from the pop-up menu. The Printer port is not designed for high speed input, so you may experience problems at high speeds.
The Terminal Setup dialog allows you to set the terminal attributes you want MacComCenter Plus to use. The Terminal Setup dialog is available by selecting Terminal from the Setup menu.
Local echo -- The Local echo option tells MacComCenter Plus to display all keyboard entries directly to the Terminal Window rather than let the remote computer echo the keystrokes back as is normal. If you cannot see what you type, turn this option on. If characters appear double (lliikkee tthhiiss) turn this option off.
Destructive backspace -- This option instructs MacComCenter Plus to erase a character when the backspace key is pressed. When this option is not selected, pressing the backspace key will move the cursor back one character but will not erase the character that may be above the cursor.
Option sends control -- When this option is selected, pressing the Option key is the same as pressing the Ctrl key.
' is ESC key -- When this option is selected, pressing the 'key (located in the upper left corner of the keyboard) will cause MacComCenter Plus to send an Escape character to the remote computer. This option is useful for keyboards that do not have an Esc key.
On-Line on startup -- When this option is selected, MacComCenter Plus will automatically go on-line and open the Terminal Window when launched.
LF after CR -- This option tells MacComCenter Plus to translate all outgoing and incoming carriage returns to carriage return + line feed.
Line wrap -- This option tells MacComCenter Plus to issue a carriage return + line feed if more than 80 characters are received on a single line.
Block cursor -- The default MacComCenter Plus cursor is a block cursor. If not selected, the cursor will be an underscore.
Blinking cursor -- By selecting this option, you may change the cursor to a blinking cursor.
Off-Line after hangup -- When this option is selected, MacComCenter Plus will automatically close the Terminal Window and go off-line when you select Hang Up from the Data menu to terminate a data call.
Scrollback buffer size -- This options defines the number of screens that will be stored in Scrollback memory. During an on-line session text may pass from the screen and scroll out of view. This option sets aside memory to enable you to scroll up (back) through the text.
Background color This option allows you to change the background color on the Terminal Window.
Foreground color This option allows you to change the foreground color on the Terminal Window
Note: These options are disabled ("grayed out") on Macs running in black-and-white mode.
Point size This option allows you to change the point size of the Terminal Window text.
Terminal emulation type On the bottom of the dialog is a line that specifies the current terminal emulator being used. This pop-up menu allows you to change the terminal emulator. MacComCenter Plus supports Teletype (TTY), DEC VT100, DEC VT102, DEC VT52 and ANSI terminal emulation. Terminal emulation is the ability of MacComCenter Plus to make your Macintosh look like a specific type of terminal to a remote computer.
VT100 Answer Back Message This allows you to enter a string that will be sent to a called machine at the beginning of a data communication session when the VT100 terminal emulator is used.
![[Data Phonebook]](/file/23826/Macworld (1998-10).dmg/Serious Demos/MacComCenter™ 3.0/MCC 3.0 Retail Online Help/Media/MCC Terminal/TerminalPhonebook.gif/TerminalPhonebook.gif)
![[Edit]](/file/23826/Macworld (1998-10).dmg/Serious Demos/MacComCenter™ 3.0/MCC 3.0 Retail Online Help/Media/MCC Terminal/TerminalPhonebookDetail.gif/TerminalPhonebookDetail.gif)
![[Dialer]](/file/23826/Macworld (1998-10).dmg/Serious Demos/MacComCenter™ 3.0/MCC 3.0 Retail Online Help/Media/MCC Terminal/TerminalDialPad.gif)
![[Protocols]](/file/23826/Macworld (1998-10).dmg/Serious Demos/MacComCenter™ 3.0/MCC 3.0 Retail Online Help/Media/MCC Terminal/TransferStatus.gif)
![[Time Elapsed]](/file/23826/Macworld (1998-10).dmg/Serious Demos/MacComCenter™ 3.0/MCC 3.0 Retail Online Help/Media/MCC Terminal/TransferProtocolsMenu.gif/TransferProtocolsMenu.gif)
![[File Transfer]](/file/23826/Macworld (1998-10).dmg/Serious Demos/MacComCenter™ 3.0/MCC 3.0 Retail Online Help/Media/MCC Terminal/FileTransferSetup.gif)
![[Modem Setup]](/file/23826/Macworld (1998-10).dmg/Serious Demos/MacComCenter™ 3.0/MCC 3.0 Retail Online Help/Media/MCC Terminal/ModemSetup.gif)
![[Terminal Setup]](/file/23826/Macworld (1998-10).dmg/Serious Demos/MacComCenter™ 3.0/MCC 3.0 Retail Online Help/Media/MCC Terminal/TerminalSetup.gif)