.l :10i .xt:1 .n :1 .x :5 Backdoor Reference Manual - Version 1.0 Intrinsic Computer Systems 29 Ridge Road Oak Ridge, NJ 07438 (201) 697 - 0174 2 .h :...Backdoor Reference Manual - Version 1.0 .h : .h : .h : .f : .f : .f : .f : .f : .f : .f : .f :...Page $$$ LICENSE All versions of Intrinsic's Backdoor are not public domain software, nor are they free software. Backdoor is copyright (C) 1988,1989 by Intrinsic Computer Systems Non-registered users are granted a limited license to use Backdoor on a trial basis for the purpose of determining whether the program is suitable for their needs. Use of Backdoor, except for this limited purpose, requires registration. Use of non-registered copies of Backdoor by any person, business, corporation, governmental agency or other entity institution is strictly forbidden. Registration permits a user the license to use Backdoor. A registered user may use the program on a different computer, but may not use the program on more than one computer at the same time. No user may modify Backdoor in any way,including but not limited to decompiling, disassembling or otherwise reverse engineering the program. All users are granted a limited license to copy Backdoor only for the trial use of others subject to the above limitations, and also the following: Backdoor must be copied in unmodified form,complete with the file containing this license information. Any and all Backdoor documentation must be included with the copy. No fee, charge or other compensation above a nominal distribution charge may be accepted or requested. If any distribution fee is charged it must not exceed $5 per disk. Backdoor may not be distributed in conjunction with any other product. 3 Operators of electronic bulletin board systems (Sysops) may post Backdoor for downloading by their users only as long as the above conditions are met. Distributors of public domain or user supported software may distribute copies of Backdoor subject to the above conditions only after obtaining written permission from Intrinsic Computer Systems. Such permission usually is granted. Please write or call for details. See the Ordering section for more information on registration, corporate licensing and similar topics. 4 WARRANTY Intrinsic Computer Systems makes no warranty of any kind, express or implied, including without limitation, any warranties of merchantability and/or fitness for a particular purpose. Intrinsic Computer Systems shall not be liable for any damages, whether direct, indirect, special or consequential arising from a failure of this program to operate in the manner desired by the user. Intrinsic Computer Systems shall not be liable for any damage to data or property which may be caused directly or indirectly by use of the program. IN NO EVENT WILL Intrinsic Computer Systems BE LIABLE TO YOU FOR ANY DAMAGES, INCLUDING ANY LOST PROFITS, LOST SAVINGS OR OTHER INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF YOUR USE OR INABILITY TO USE THE PROGRAM, OR FOR ANY CLAIM BY ANY OTHER PARTY. 5 Intrinsic Computer Systems Order Form(BD1.0) 29 Ridge Road Oak Ridge,NJ 07438 L---+---T1----+-T--2----T----3--T-+----4T---+---T5----+-T--6----r----7-RT-+--- Please send: ____ Backdoor Disk (current version) ............ @ $ 45.00 ea $ ______ (includes program and manual on disk, no registration) ____ Backdoor Registration ...................... @ $ 35.00 ea $ ______ (does not include disk) ____ Backdoor Registration and Disk Combo ....... @ $ 55.00 ea $ ______ (registration, program, typeset manual) Subtotal ______ Less Discount <______> (New Jersey residents please add 6% sales tax) Tax ______ Total $ ______ Payment by: ( ) Check ( ) Money Order ( ) PO # ______________ Name: ____________________________________________________________ Company: ____________________________________________________________ Address: ____________________________________________________________ : ____________________________________________________________ : ____________________________________________________________ Day Phone: (______)___________________ Eve: (______)_____________________ ORDERS OUTSIDE THE US: Use check or money order drawn on US bank in US dollars. Sorry, no C.O.D. orders will be accepted. 6 L---+---T1----+-T--2----T----3--T-+----4T---+---T5----+-T--6----R----7--T-+--- CHAPTER Quick Start Welcome to Backdoor. To allow you to install Backdoor as quickly as possible, simply follow the directions below. If you feel, after reading them, that you need more detailed instructions then turn to Detailed Installation Directions. This will lead you through the installation in a more thorough manner. Step 1: Install Backdoor onto your hard disk into the subdirectory you wish to keep Backdoor in. b) Copy the files from the Backdoor diskette into the Backdoor subdirectory: copy a:Backdoor.* Step 2: Run Backdoor a) Type Backdoor Step 3: Press the key labeled "Alt" and the "h" simultaneously. These are the Backdoor hot key combination. Step 4: Review the hardware settings for Backdoor. a) Use the down arrow key to move the highlighted cursor bar to "Hardware Setup" and press the return key. b) Look at the hardware settings presented. Make sure your modem is connected to the communications port number ("Com Port") as displayed. Also, verify the baud rate,data bits,parity, and stop bits. c) If you need to change one of the hardware settings, press the down arrow key to move the 7 cursor bar between the various hardware settings. When the setting you wish to change is highlighted, press the return key and enter the correct hardware setting. Finish entering your change by pressing the return key. d) To save the configuration, press the ESC key to exit to the main menu. Move the cursor bar to "Config Save" and press the return key. The hardware configuration will be saved. Step 5: Explore! Call up the other windows and see how they work. Some Hints: a) At any of the menus in Backdoor you can obtain help by pressing the F1 key. A help window will pop up to explain the various options available to you. b) When the main menu displays you may go directly to a selection by pressing the first letter of the selection. 8 CHAPTER Introduction Thanks for purchasing Backdoor! Backdoor is a file transfer and terminal emulation program. It works with Hayes compatible modems and supports three widely used file transfer protocols (Xmodem, Kermit, and Ymodem). It supports baud rates of up to 19,200. It has an ANSI compatible terminal emulator. Backdoor will automatically schedule file transfers to other Backdoor'd computer systems. You can set up Backdoor to answer your phone and receive a file in the file transfer protocol of your choice. It also, has an extensive logging facility. It does all the above while you may be running,say, any spreadsheet or word-processing package. While running your other application, you may optionally have Backdoor inform you progress of file transfer or you may directly call backdoor up to use Backdoor's other features directly. The rest of this manual is divided into sections which describes each of these features as available from the main menu of Backdoor. Once Backdoor's installed its main menu may be called up by pressing the "hot key" combination. The default hot key combination is "alt h." If you have any comments concerning Backdoor they would be greatly appreciated and can be sent to us via the above address or via CompuServe. Our CompuServe identification number is [75036,1602]. Please let us know what you are doing with Backdoor, what applications, what hardware, etc. The better we know you the better we can tailor our product to your needs. Drop us a line with a return address, phone number, business card, and brief description. 9 CHAPTER Transfer Status Window This window's used to see the statistics of the current file transfer and do some infrequent Backdoor operations. From this window you may cancel the current transfer, toggle the top of screen status bar, and remove Backdoor. The Transfer Statistics Displayed are: File Name: Contains the current file name being sent or received. If no file is transferring then this field will be blank Bytes Xfrd: Contains the accumulated bytes transferred for the current file. If the current protocol is Kermit this byte count will accumulate to a larger number than the actual file size. This is because Kermit uses a special encoding scheme that translates binary characters into two ASCII characters. Last Msg: May contain a text message describing the last error condition that has occurred. Depending on the nature of the message the error my mean the current transfer is in the process of aborting, or merely that a minor error occurred and an attempt has or will be made to recover. The list of error messages and their probable cause and meaning is in the appendix. File Xfrd so far: This field has the accumulated count since Backdoor has started of files transferred. File Xfrd since last check: This field has the accumulated count since you last called up this menu of files transferred. Actions you may do while viewing this window. Cancel Xfer: By entering a 'Y' in this field you will force Backdoor to cancel the current file transfer. Press the return, then press the 'Y' key. If you wish to escape without entering a 'Y', either press the 'N' key or press 10 the ESC key. Remove Backdoor: By entering a 'Y' into this field you will force Backdoor to attempt to remove itself from the computers memory. You may wish to do this before running large application programs or programs that may conflict with Backdoor. Please note that you cannot remove Backdoor from memory if it's not the last installed TSR, nor can you remove Backdoor if you are running an application program. To remove Backdoor move the highlighted arrows to this field and press the return key. Then press the 'Y' key. If you wish to escape without entering 'Y', either press the 'N' key or press the ESC key. If you enter 'Y' Backdoor will display a warning window. This warning window will prompt you to press a key. Once you press a key,if Backdoor can remove itself it will remove its windows, if not it will display an error message. Status Bar: By entering a 'Y' into this field you will allow a status bar to display at the top of the screen. This status bar shows the current file name transferring, the number of bytes transferred, a status code (see appendix), and the protocol in use. If you enter a 'N' into this field the status bar will not display. To change the status bar display status move the highlighted arrows to this field and press the return key. Then press the 'Y' or 'N' depending if want a status bar or not. If you wish to escape without changing the current setting either press the 'N' key or press the ESC key. 11 CHAPTER Misc Setup Window This window's used to set your autoanswer protocol type, the directory to place received files into, the directory from which files to send out from, and the key combination to start up Backdoor. You may wonder why the send/receive directories must be specified. The reason is, that since Backdoor is running in the background while an application is active, the current directory may be changed without Backdoor noticing it. If the current directory changes Backdoor may lose a file its in the process of transferring. Therefore, a fixed directory must be used by Backdoor. A change to the hot key field does not come into effect unless you save the current configuration (See Main Menu Save Config choice). The other fields changes do not become permanent unless you save the current configuration, but they do become the current until you remove Backdoor or reboot your computer. The Misc Setup Fields are: Receive Directory: This field shows the current directory that will receive files. To change the directory, move the highlighted arrows to this field and press the return key. Then enter the directory name that you wish to use for received files. If while entering the directory name you wish to escape without changing the current setting press the ESC key. When you do enter a directory name Backdoor will check to see if the directory exists. If it doesn't Backdoor will present an error window informing you of this. Protocol: This field shows the current default protocols for receiving a file. To change the default protocol move the highlighted arrows to this field and press the return key. Then enter the protocol name that you wish to use for received files. You may use the up/down arrow keys to have Backdoor present the different protocols available if you choose. If while entering the default protocol you wish to 12 escape without changing the current setting press the ESC key. When you do enter a directory name Backdoor will check to see if the protocol is a valid one. If it isn't Backdoor will present an error window informing you of this, and revert to using the previous entry of this field. Send Directory: This field shows the current directory that will be used to send files. To change the directory, move the highlighted arrows to this field and press the return key. Then enter the directory name that you wish to use for sending files. If while entering the directory name you wish to escape without changing the current setting press the ESC key. When you do enter a directory name Backdoor will check to see if the directory exists. If it doesn't Backdoor will present an error window informing you of this, and revert to using the previous entry of this field. Hot Key: This is really two fields. You can use this field to change the hot key combination that will start Backdoor. This may be needed if Backdoor's hot key combination conflicts with other TSR programs. Once this field changed, the hot key combination will not come into effect until you save the current configuration, remove Backdoor and restart it. To change the hot key combination, move the highlighted arrows to either one of these fields and press the return key. You may use the up/down arrow keys to have Backdoor present the different hot keys available. Or you may enter directly in the hot key name that you wish to use for starting Backdoor. 13 CHAPTER Upload Setup Window In this window you set up for files to be automatically uploaded to other computers using Backdoor. In each row of this window you enter the date/time, the telephone number to call, the communications settings, and the filename to send. In this window by pressing the down arrow key the highlight arrows will highlight the entire row. If you press the down arrow until the highlight bar reaches the bottom of the window and continue to press down, more rows will scroll up. To modify fields within a row press the right arrow, or the return key. Then move the highlight arrow to the field you wish to change. The Upload Setup Fields are: Date: This is actually three fields next to each other. The fields are in month,day, and year order. To change the date, move the highlighted arrows to either one of these fields and press the return key. Enter directly in the number you wish to use. When you do enter a date Backdoor will check to see if the date is in the future. If it isn't Backdoor will present an error window informing you of this, and revert to using the previous entry of this field. Time: This is actually two fields next to each other. The fields are in hour - minute order. To change the time, move the highlighted arrows to either one of these fields and press the return key. Enter directly in the number you wish to use. When you do enter a time Backdoor will check to see if the time is in the future. If it isn't Backdoor will present an error window informing you of this, and revert to using the previous entry of this field. Baud: In this field you put in the baud rate of the receiving computer. Please note that your modem must also support this baud rate. Most modems support a range of baud 14 rates, and most will automatically adjust downward to the incoming modem's. You must enter the baud rate that will be used during the transfer of files, not the baud rate the other computer will 'answer' at. To change the baud rate move the highlighted arrows to either one of these fields and press the return key. You may use the up/down arrow keys to have Backdoor present the different baud rates available. Or,you may enter directly in the number you wish to use. If while entering the number you wish to escape without changing the current setting press the ESC key. When you are finish entering the baud rate press the return key. When you do enter a baud rate Backdoor will check to see if the baud rate is valid. If it isn't Backdoor will present an error window informing you of this, and revert to using the previous entry of this field. D, P, & S fields: These fields are the Data Bits, Parity, and Stop bit fields. Usually, these are 8,N, & 1. However, some computer systems set them differently so be safe and ask. To change the these fields move the highlighted arrows to either one of these fields and press the return key. You may use the up/down arrow keys to have Backdoor present the different possible field contents available. Or,you may enter directly the text you wish to use. If while entering you wish to escape without changing the current setting press the ESC key. When you are finish entering press the return key. Protocol: In this field you enter the file transfer protocol to use to send the file. To change the protocol, move the highlighted arrows to this field and press the return key. Then enter the protocol name that you wish to use. 15 You may use the up/down arrow keys to have Backdoor present the different protocols available if you choose. If while entering the protocol you wish to escape without changing the current setting press the ESC key. When you do enter a protocol name Backdoor will check to see if the protocol is a valid one. If it isn't Backdoor will present an error window informing you of this, and revert to using the previous entry of this field. Telephone #: In this field you enter the telephone number of the other Backdoor computer. To change the telephone number, move the highlighted arrows to this field and press the return key. Then enter the telephone number that you wish to use. If while entering the telephone number you wish to escape without changing the current setting press the ESC key. Filename: In this field you enter the filename to send to the other Backdoor computer. To change the filename, move the highlighted arrows to this field and press the return key. Then enter the file name you wish to send. If while entering the filename you wish to escape without changing the current setting press the ESC key. 16 CHAPTER Hardware Setup Window In this window you set up the hardware settings for your communications port. The communications port is how the IBM PC talks to your modem. Your modem is how your computer interfaces to the telephone system and finally to the other computer. The Hardware Setup Fields are: Com Port: The communication port is usually 1 or 2. If you have an internal modem the port the port number must still be set as the modem itself looks like a port to Backdoor. Baud Rate: The baud rate field should match the baud rate of the modem you will be using. Usually, this will be 2400 baud. However, baud rates from 300 to 19,200 baud are supported. The faster the baud rate the more pauses you will notice during a file transfer since Backdoor is working with a higher volume of data. Data Bits: This field is usually 8 and refers to the number of bits per character of data sent over the serial port or modem. The reason you may wish to change this is that this setting should match the data bits of the modem or computer system you will be connecting to. Some systems use 7 data bits. To be absolutely sure of what the data bits are, ask the owner of the other system. Parity: This field refers to weather if any modem error detection is done. There is no real standard setting for this. It is possible to connect to another computer at a different parity setting but usually the file transfer will not work. Stop Bits: This field is usually 1 and refers to the number of bits that indicate the end of a character. 17 Modem Init String: The modem initialization string usually begins with "AT." The actual string depends on the modem type. Backdoor, supports Hayes or Hayes-compatible modems only. Fortunately, most intelligent modems are Hayes compatible. If you are using the modem at home the string should be ATD. The "AT" is the modem attention string, the "D" is the modem dial command. Backdoor uses this string to issue dial commands to the modem. If you are using this on a telephone system where you need to dial a number to get to an outside line the modem string should look something like this "ATD9." Where the digit "9" would be replaced by the actual number you need to dial out with. If you intend to only dial long distance numbers then you may append the digit one onto modem string. If you wish to dial long distance and local numbers do not put in the long distance prefix in this field. Prefix all your telephones (in other Backdoor fields) with a one. 18 CHAPTER Config Save Window Choosing this option will save the current configuration. The current configuration is : Dial Number (As used in Terminal Mode)  Hardware Settings (Defined in Hardware Setup)  Hot Key Combination (Defined in Miscellaneous Setup)  Modem Init String (Defined in Hardware Setup)  Protocol (Defined in Miscellaneous Setup)  Receive Directory (Defined in Miscellaneous Setup)  Send Directory (Defined in Miscellaneous Setup)  Status Bar (Y/N) (As defined in Transfer Status) 19 CHAPTER Save Schedule Window When this option's selected the current schedule as setup in upload setup is saved. Next time Backdoor is loaded it will load in the schedule. If the scheduled has any files scheduled for a future time Backdoor will send them at the scheduled time. 20 CHAPTER Review Log Window When this option's selected you may review Backdoor's log file. This log file contains status messages written by Backdoor. Each message is date and time stamped so you can see when the message was written. To review the file, simply press any key and it will scroll through the log file. Press the ESC key to exit. Messages are written on the following condition. Abort of a file transfer  End of a file transfer  Start up of a file transfer  Time Out  Unable to open file 21 CHAPTER Virtual Terminal Window When this choice's selected a partial screen virtual terminal will appear. This terminal emulation is a subset of an ANSI terminal. It supports simple cursor movement, line and screen clears. The terminal mode is usually a window that you can "pop"up on the screen that will act like a "dumb" terminal. Characters received during terminal mode while the terminal window is not up are saved in an internal buffer. So, when you call up the terminal window you will see the characters received since you last looked at the terminal window. One important note about terminal mode is that upon calling up the virtual terminal you remain in terminal mode until the hang- up key is pressed. Even if you exit, the virtual terminal (Alt- x) you will be still in terminal mode. If you are in terminal mode you cannot automatically receive file transfers from other Backdoor systems - you must press the hang-up key combinations (Alt-h). While in terminal mode the following special keys are defined: Key Description Alt-d Dial a number  Alt-e Echo characters  Alt-g Capture screen  Alt-h Hang-up phone  Alt-k Script invocation  Alt-p Change port settings  Alt-x Exit While in terminal mode you may start a file transfer by pressing the PAGE UP or PAGE DOWN keys for sending or receiving. Press the Alt-X key combination to exit the terminal mode. 22 Press the Alt-G key combination to capture a copy of the terminal screen to a Backdoor.SCR file. Press the Alt-P key combination to change the current port or its settings (baud rate, parity, etc.). To have Backdoor "echo" characters as typed in, press Alt-E combination. To dial out press the Alt-D combination and enter the telephone number to dial, or on a Hayes' compatible modem type ATDXXXXXXX where X is the telephone number. To hang-up and exit the terminal into modem mode, press Alt-H. Hanging-up is the only way to exit from the terminal mode into the modem mode. Alt-k is used to start a script file up. Type in the full name of the script file including extension. To abort or exit a script file, press the ESC key. Script file commands are described in the appendix. 23 CHAPTER How To Set Up For Autoanswer When Backdoor is loaded it automatically sets up the modem for autoanswer. Then Backdoor goes into "Modem" mode. You can see what mode Backdoor is in by looking at the status bar. When Backdoor is in modem mode it will continuously wait for a character to be received on the port. Once it detects a character it will go into the default receive protocols' receive sequence. For Xmodem this means, that Backdoor will start sending a NAK character. When in modem mode Backdoor will wait for the telephone to ring (assuming you have a modem), and then enter into receiving a file when the other system "connects" with your modem. Warning! When you start up the virtual terminal from the menu, Backdoor exits the modem mode and enters the "terminal" mode. To restore the modem mode from the terminal mode, simply hangup (alt-h) will in the virtual terminal. Backdoor will change the mode to modem. The reason the modem mode is lost once you enter the terminal mode is that once you enter the terminal you may wish to maintain it in that mode( even if you resume working on your foreground application). Backdoor has no way of "knowing" what your intentions are and therefor we designed it such that you have to explicitly tell Backdoor. 24 CHAPTER Detailed Installation Directions These detailed instructions are for installing Backdoor onto your hard disk. Step 1: Boot up your computer: Step 2: Next at the DOS prompt create the Backdoor subdirectory on your hard disk. The Backdoor subdirectory name may be of your own choosing or even an existing one. However, we recommend that Backdoor be put in its own subdirectory if for no other reason but to keep it separate. Once you choose where in your hard disk's directory structure to put the new directory, move to its parent's directory via DOS's CD command and use the following DOS command to create the new directory: mkdir Backdoor Step 3: Next move to the new directory by typing: cd Backdoor Step 4: Copy the files from the Backdoor diskette (we assume its in the A drive) into the Backdoor subdirectory by typing the following command: copy a:Backdoor.* Step 5: To Run Backdoor type: Backdoor 25 APPENDIX How Backdoor Works Backdoor belongs to a class of programs called "Terminate and Stay Resident (TSR)". It installs itself and becomes part of your computers, memory - not permanently though! Backdoor works in the "background" while another program is working in the "foreground." This "background/foreground" stuff merely means that while a program you are using is running, Backdoor is periodically run. Backdoor, when it does run, usually runs for only a few tenths of a second. However, depending on such things a whether you're doing a file transfer, how fast your disk and computer are, Backdoor will consume more time. This may be as much as a few seconds. During these occasions the computer may appear to pause. Don't worry! Backdoor is merely do something in the "background" and will return the computer to the "foreground" application as quickly as possible. 26 APPENDIX Scripting Scripting's intended to allow you to create script files for automated sign on to the remote systems that you use. To create a script file use your word processor (in its straight ASCII mode) or EDLIN (comes with DOS). Script file commands are very simple and will work in 95% of all cases. The commands may be upper or lower case, and may have leading white space. You may also have blank lines. The commands are as follows: WAITFOR "XXXXXXXXXXXXXXXXXXXXXXX" Where "XXXXX..." is the string to wait for. Control characters are denoted by preceding them by the caret '^' symbol. For example to wait for "USERNAME:" where there is a carriage return after the user name string use the following: WAITFOR "USERNAME:^M" Please note the quotes around user name are part of the syntax of WAITFOR and must be included. If part of the string you wish to wait for has a double quote character then put two double quotes in the string. WAIT NNNN Waits for NNNN seconds. Pauses execution of a script file for NNNN seconds. You cannot escape from this command. This command is useful in situations where a pause may occur on the other system. You therefore may wish to wait for a few seconds. As an example to wait for 300 seconds (5 minutes) the command would be: WAIT 300 27 SEND "XXXXXXXXXXXXXXXX..........X" This command sends the string "XXXXXXXXXXX...X" to the remote string. The string may contain control characters as the WAITFOR string can. As an example to send a password sign on the following might be sent: SEND "YOURNAME^N" DIAL NNNNNNNNNNN This command dials the number NNNNNNN. Note the NNNNN number may contain commas or dashes. For example to dial the long distance number 201-430-7700 the following would be used: DIAL 1-201-430-7700 # This command simply allows comments be inserted in your script files. Any text on the same line, following the pound sign will be ignored. 28 APPENDIX Error Codes and Messages The following is a list of the possible error numbers that will appear on the top of screen bar, and the corresponding error message in the status window. Under each message is a brief explanation of what it means and possible causes and corrective actions (if necessary). Error Message 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 1 Record header mismatch 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�  During a file transfer the header of a packet had a mismatched sequence number. 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 2 CRC error 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�  During a file transfer the CRC check failed for a packet. 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 3 Buffer full 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�  During a file transfer the internal buffer of Backdoor filled up. This means that Backdoor didn't have a chance to empty its buffer to disk. A possible reason is that the foreground program was doing extensive disk activity (such as formatting a disk). Or that the directory that Backdoor puts it files to is full or inaccessible (does Backdoor think its directory is on a floppy which is no longer in the floppy?) 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 4 Buffer empty 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�  29 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 5 Invalid record header 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� During a file transfer a packet was received with an invalid record header. 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 6 Time out 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�  During a file transfer the other side failed to send a recognizable packet or did not send any packet at all during a fixed period. 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴 7 Xfer aborted by other end 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴  During a file transfer the transfer was aborted by the other computer. This may have occurred because of the other side not having enough disk space or by the other sides operator. 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 8 Can't open file - Fatal 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�  During a file transfer Backdoor was unable to open the file it was to send or unable to open the file it was creating( during a receive). 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴 9 Can't write file - Fatal 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴  During a file receive Backdoor was unable to write to the file. This may be because of the disk is full or Backdoor is unable to access the file (floppy door open?). 30 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 10 Port hardware error 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�  This occurs when a parity error, overrun, or framing error's detected on the port. Corrective action is sometimes unnecessary since errors due occur on telephone lines. If this error is recurring rapidly such as several times a second, then probably your port hardware settings (or the other computers) is incorrect. 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 11 Invalid packet type - Fatal 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�  During a file transfer (usually a Kermit transfer) a packet was received whose packet type wasn't expected. This usually suggests a severe synchronization problem exists between the two computers and therefor is irrecoverable. Backdoor will send an abort file transfer to the other computer. 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴 12 Unable to synch up - Fatal 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴  At the beginning of a file transfer Backdoor was unable to start the exchange of file packets. 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴 13 Record out of sequence - Fatal 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴  During a file transfer Backdoor got a packet with a sequence number out of order. This usually suggests a severe synchronization problem exists between the two computers and therefor is irrecoverable. Backdoor will send an abort file transfer to the other computer. 31 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴 14 Communication Interrupt Stolen 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴  When Backdoor starts up it re-vectors the communications ports interrupt to itself. If while Backdoor is in the background another communication program is run in the foreground, the foreground program will re-vector the communications interrupt to itself. Backdoor will detect this and while the foreground communications program is actively using the communications interrupt Backdoor will do nothing (other than show this error code). After the foreground program releases the communications interrupt, Backdoor will re-vector the interrupt to itself. 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 15 Transferred OK  컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�  At the end of a successful file transfer, Backdoor will show this message. 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 16 Packet Resent  컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�  If during a file transfer a minor error's detected, the usual course of action is to resend the packet.