ClientServerArch

Question 1

Server Types

Answer 1

1-DNS server
match domain names to I.P. addresses

2-Proxy server
an intermediary server separating end-users from
websites they browse

3-Mirrored server
hold the same data as another server in order to be a
backup and to reduce traffic

4-Web server
hosts web sites

5-E-mail server
receives and sends email messages

6-List servers
manages mailing lists to groups of e-mail addresses,
distributing e-mails to everyone on the list

Question 2

Server Definition

Answer 2

• Computer providing services to client requests. It must have the power, speed and storage to be able to handle multiple requests from clients
• A software that delivers data on request

Question 3

Web Server

Answer 3

Accept HTTP requests from clients (e.g. browsers) and serve them HTTP responses (with optional data in the body, which is typically the requested resource)

Question 4

When you navigate to a URL:

Answer 4

1-CLIENT: You type a URL in the address bar and hit “enter”

2-Browser sends an HTTP GET request saying
“Please GET me the index.html file at http://cs193x.stanford.edu”

3-Browser C++ code creates an array of bytes that is formatted in using
HTTP request message format

4-Browser asks operating system, “Hey, can you send this HTTP GET request message to http://cs193x.stanford.edu”?

5-Operating system sends a DNS query to look up the IP address of “http://cs193x.stanford.edu”

6-DNS server replies with the IP address, e.g. 171.67.215.200

7-Operating system opens a TCP connection with the computer at
171.67.215.200

8-After the TCP connection is established, the OS can send the HTTP message to 171.67.215.200 through the TCP connection

Question 5

port

Answer 5

port: In the context of networking, a “logical” (as opposed to a physical) connection place

A number from 0 to 65535 (16-bit unsigned integer)

Question 6

binding

Answer 6

When you start running a process, the operating system associate a port number with it. This is called binding

Question 7

A TCP connection requires an ………. and a ……….

Answer 7

A TCP connection requires an IP address and a port number

Question 8

If no port number is specified, ….. is the default for HTTP requests

Answer 8

80 is the default for HTTP requests

Question 9

When a server computer receives a message:

Answer 9

1-Operating system opens a TCP connection on port 80 of the computer at
171.67.215.200

2-The server process running on port 80 is responding to requests

3-Now the operating system is receiving TCP packets from the wire, and the operating system begins sending the contents of the request to the server program

4-The server software parses the HTTP request and then decides what message it wants to send in response. It formats this message in HTTP

5-The server sends back a status line, such as “HTTP/1.1 200 OK”, and a message of its own. The body of this message is typically the requested resource, although an error message or other information may also be returned

6-This HTTP response is then sent back to the client’s OS, which notifies the browser of the HTTP response, and then the browser displays the web page