**** Online communication: remote login and file transfer

Transcription

1 **** 1 Online communication: remote login and file transfer by Paul.Nieuwenhuysen@vub.ac.be 2005 More elaborate and up to date study materials should be available from the WWW site of the author:

2 **** 2 Online communication: remote login and file transfer Introduction

3 **** 3 Online communication: summary 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.

4 **** 4 Online communication: prerequisites Before using online communication systems, you should ideally have some knowledge and skills related to computer hardware computer software the Internet

5 **** 5 Online communication: remote login and file transfer Remote terminal log-in / access

6 **** 6 Remote terminal log-in / access: definition 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.

7 **--Examples 7 Remote terminal log-in / access: examples of terminal emulation No emulation: ASCII or TTY (teletype) Digital Equipment Corporation / DEC video terminals VT52, VT100, VT200,... IBM IBM 3270,......

8 ***- 8 Online communication: remote login and file transfer Serial line data communication software

9 ***- 9 Remote terminal log-in / access: summary 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).

10 **-- 10 Serial line data communication software packages 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»...

11 **** 11 Online communication: remote login and file transfer Telnet in the Internet

12 **** 12 Telnet: description 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

13 ***- 13 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,...)!

14 ***- 14?? Question?? Which client program do do YOU use for telnet?

15 ***- 15!! Task - Assignment - Exercise!! Make a telnet connection with a remote telnet server computer.

16 **** 16 Online communication: remote login and file transfer Downloading and file transfer

17 ***- 17 Data communication: downloading 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).

18 ***- 18 Data communication: downloading methods 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)

19 **** 19 Data communication: downloading by copying a fragment 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.

20 ***- 20!! Task - Assignment - Exercise!! Capture some information displayed by by a remote computer, using select, copy and paste.

21 **-- 21 Data communication: downloading to a log file 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.

22 **** 22 Online communication: remote login and file transfer File transfer ftp in the Internet

23 **** 23 Data communication: file transfer Copying + downloading / transfer of a whole file Requires a transfer protocol with error correction

24 ***- 24 ftp: file transfer protocol in the Internet 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.

25 ***-Examples 25 ftp: client programs for Windows Primitive ftp program included in Windows 95, 98, (several files at the time) WS_ftp Netscape Microsoft Internet Explorer... (several files at the time) (only 1 file at the time) (only 1 file at the time)

26 ***- 26?? Question?? Which ftp ftp client program do do YOU use?

27 ***- 27!! Task - Assignment - Exercise!! Copy a file from a remote computer to to your own computer, using ftp; for for instance from ftp://ftp.vub.ac.be/

28 **-- 28!! Task - Assignment - Exercise!! 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/

29 **-- 29 Online communication: remote login and file transfer Conclusion

30 **-- 30 Online communication: from remote login to file transfer 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

31 **-- 31 Online communication: summary 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