Cirrus Logic CS485 Bedienungsanleitung PDF herunterladen (Seite 65)

CS485G Spring 2015 65

59 Client-server

1. Clients

(a) Examples: ftp, telnet, ssh, browsers like Firefox.

(b) Lecture 37, 5/1/2015

an IP address.

(d) To ﬁnd the right port: look int /etc/services to ﬁnd the stan-

dard port for various services, such as 25 (smtp), 80 (http).

2. Servers

(a) Typically long-running, started when the operating system boots.

(b) Can be stopped/started, by distribution-dependent methods (such

as service apache2 stop.

with a standard protocol (typically on top of TCP).

(d) Standard services. Each uses a

i. Web (80/HTTP): provides ﬁles, can perform server-side com-

putation (SHTML, CGI, PHP, JSP, ...).

ii. FTP (20, 21/FTP): stores and retrieves ﬁles.

iii. Telnet (23/Telnet): interactive login. Deprecated, because

unencrypted.

iv. SSH (22/SSH): interactive login; encrypted.

v. Mail (25/SMTP): accepts incoming mail.

3. Web services

(a) The WWW mostly started around 1993, with the Mosaic browser;

there were about 200 WWW servers worldwide.

(b) Web servers return content to clients, which is a sequence of

bytes tagged with a MIME (Multipurpose Internet Mail Exten-

sion) type, such as text/html, application/pdf, image/png.

on demand).

(d) Each content item is associated with a URL (Universal Resource

Locator), of a general form service://host:port/file/

path, speciﬁcally http://www.cs.uky.edu/

raphael/courses/

CS485/index.html

1 2 ... 60 61 62 63 64 65 66 67

Keine Kommentare

Cirrus Logic CS485 Bedienungsanleitung Seite 65