Online communication: remote login and file transfer

Transcription

1 **** 1 Online communication: remote login and file transfer Introduction **** Online communication: summary 2 The following gives an overview of the classical, older, well established techniques to communicate online with a remote computer. 1. First comes login into a remote computer to use some information source or facility offered by that computer. 2. Then comes transferring/copying files online from one computer to another.

2 **** Online communication: prerequisites 3 Before using online communication systems, you should ideally have some knowledge and skills related to computer hardware computer software the Internet **** 4 Online communication: remote login and file transfer Remote terminal log-in / access

3 **** Remote terminal log-in / access: definition 5 The ability to access a computer from outside a building in which it is housed. This requires communications hardware, software, and actual physical links, although this can be as simple as common carrier (telephone) lines or as complex as telnet login to another computer across the Internet. **--Examples Remote terminal log-in / access: examples of terminal emulation 6 No emulation: ASCII or TTY (teletype) Digital Equipment Corporation / DEC video terminals VT52, VT100, VT200,... IBM IBM 3270,......

4 7 Online communication: remote login and file transfer Serial line data communication software ***- ***- Remote terminal log-in / access: summary 8 An interactive process in which you give a command, get a response, give a counter-response, and so on. Your microcomputer acts as a terminal to another computer. This may require terminal emulation. The remote computer might be anywhere on the network (in your institute, across the country, or across the world).

5 **-- Serial line data communication software packages 9 Software packages to communicate with a remote computer from your own microcomputer through a serial line, exist for many types of microcomputer systems, such as»a PC using DOS (without Microsoft Windows)»a PC using Microsoft Windows»a Macintosh»... *---?? Question?? 10 In In the case that YOU have some experience with serial line data communication, which software package have you used?

6 *---Examples Serial line data communication software for DOS (no Windows) 11 Bitcom Crosstalk Kermit (not = the file transfer protocol Kermit) Procomm Relay Smarterm Telix... *---Examples Serial line data communication software for Windows (Shareware) 12 Terminal (included in Microsoft Windows 3.x) Hyperterminal (included in Microsoft Windows 95) Unicom for Windows Win Kermit WinQVT WinVT100...

7 *---Examples Serial line data communication software for Windows (Commercial) 13 Terminal Plus and Dynacom for Windows Crosstalk for Windows Keaterm Microphone for Windows Procomm for Windows Relay for Windows... *--- Data communications software: automating remote login 14 Configuration files (for instance.trm for Windows Terminal) One or several dialing directories Buttons (in GUI s) or programmed key combinations (in DOS) Scripts = macro s... + links among these

8 **** 15 Online communication: remote login and file transfer Telnet in the Internet **** Telnet: description 16 The Internet standard protocol for remote terminal connection service; on top of the TCP/IP protocol suite Allows a user at one site to interact with a remote timesharing system at another site as if the user's terminal was connected directly to the remote computer Includes VT100 terminal emulation

9 ***- 17 Telnet: available client programs Client programs which allow a remote login according to the telnet protocol with telnet servers, are available for most operating systems, including»[unix ( telnet,...)]»apple»[dos (e.g. NCSA telnet ; telnet programs included in TCP/IP packages)]»windows (e.g. telnet programs included in TCP/IP packages and in Windows 95 and later versions, EWAN, Procomm, WinQVT,...)! * Telnet: character-based user interface for Unix and DOS client program Some important commands in a typical program with a character-based user-interface:»open connection telnet computer_address»quit / exit telnet telnet> quit or telnet> exit

10 ?? Question?? 19 Which client program do do YOU use for telnet? ***- ***-!! Task - Assignment - Exercise!! 20 Make a telnet connection with a remote telnet server computer.

11 **** 21 Online communication: remote login and file transfer Downloading and file transfer ***- Data communication: downloading 22 The electronic transfer of information (whole file or fragments) from one computer to another, generally from a larger computer to a smaller one (such as from a server under Unix to a microcomputer).

12 ***- Data communication: downloading methods 23 The method used depends on the amount of the information which is displayed that has to be captured:»copying a small fragment!»(storing a large part in a log file) **** Data communication: downloading by copying a fragment 24 Capturing a small fragment of the information displayed: 1. select information on the display, 2. copy, and 3. paste in a document managed by another program.

13 ***-!! Task - Assignment - Exercise!! 25 Capture some information displayed by by a remote computer, using select, copy and paste. **-- Data communication: downloading to a log file 26 Capturing a large part of the information displayed: 1. open a log file, to capture the information, 2. close the log file, 3. open the log file with a program to view it.

14 *---!! Task - Assignment - Exercise!! 27 Capture some information displayed by by a remote computer, by by creating a log file. **** 28 Online communication: remote login and file transfer File transfer ftp in the Internet

15 **** Data communication: file transfer 29 Copying + downloading / transfer of a whole file Requires a transfer protocol with error correction *--- Protocols for error correction during file transfer 30 A version of the protocol (program) runs at both computers, during file transfer. Name of protocol ASCII = text (= no program) Xmodem Ymodem Zmodem Kermit (ASCII / binary) ftp (ASCII / binary) Error correction Applications Public databanks BBS BBS BBS BBS Internet

16 *--- Kermit user interface on Unix: important commands 31 kermit kermit>set file type ascii kermit>send interesting_text_file kermit>exit kermit kermit>set file type binary kermit>send interesting_binary_file kermit>exit ***- ftp: file transfer protocol in the Internet 32 A high-level protocol = application protocol in the Internet. For transferring files from one computer to another (free of errors). Provides the capability 1. to connect to a remote computer, 2. to execute a few simple tasks (such as listing the directory), 3. to copy files to or from the remote computer quickly.

17 *--- ftp: client program for Unix 33 First log into a Unix computer and start a Unix ftp program. *--- ftp: client programs for DOS 34 Included in most of the TCP/IP-based LAN NFS packages for DOS Included in the CUTCP bundle of programs...

18 *--- ftp: character-based user interface of ftp client programs 35 Making the connection When connected ftp computer_address ftp>help or? ftp>cd pub ftp>ls or dir ftp>binary ftp>prompt off ftp>get interesting_file OR ftp>mget interesting_files ftp>bye or quit ***-Examples ftp: client programs for Windows 36 Primitive ftp program included in Windows 95, 98, (several files at the time) WS_ftp (several files at the time) Filezilla (several files at the time) Netscape (only 1 file at the time) Microsoft Internet Explorer (only 1 file at the time)...

19 ?? Question?? 37 Which ftp ftp client program do do YOU use? ***- ***-!! Task - Assignment - Exercise!! 38 Copy a file from a remote computer to to your own computer, using ftp; for for instance from ftp://ftp.vub.ac.be/

20 **--!! Task - Assignment - Exercise!! 39 Copy (in (in one action) a few files from (or to) to) a remote computer to to (or from) your own, using ftp; for for instance from ftp://ftp.vub.ac.be/ **-- 40 Online communication: remote login and file transfer Conclusion

21 **-- Online communication: from remote login to file transfer 41 Remote login without downloading Remote login with downloading, but only ASCII, without explicit error correction protocol Remote login with file transfer, using an error correction protocol such as kermit or Xmodem or Zmodem File transfer only, using a suitable client program **-- Online communication: summary 42 User + Microcomputer Communication network (telephone; public access data communication; Internet;...) Basic data communication protocols (X-25; TCP/IP;...) Application protocols and software (Kermit; X-modem; Y-modem; Z-modem; telnet and ftp in Internet;...) External host computer

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