Chapter 11, Problem 11.6HW

A.

Program Plan Intro

IP addresses:

• The IP address denotes an unsigned integer that is 32-bit.
• The IP addresses is been stored by network programs in IP address structure.
• The addresses present in IP address structure are stored in network byte order.
• An unsigned 32-bit integer is transformed from host byte order to network byte order by “htonl” function.
• An unsigned 32-bit integer is transformed from network byte order host byte order by “ntohl” function.
• The IP address is presented to humans in a form known as “dotted-decimal” notation.
  • Each byte is been represented by its corresponding decimal value and is separated by a period from other bytes.

Passing program arguments to server:

• The arguments for “GET” requests are passed in the URI.
• The character “?” separates filename from the arguments.
• The character “&” separates each argument.
• The arguments do not allow spaces in it.

Server passes arguments to child:

• The server calls “fork” to create a child process and calls “execve” to run program in child’s context once it receives a request.
• The child process sets CGI environment variable values.
• The “adder” program can reference it at run time using “getenv” function of linux.

Output is sent by child:

• The dynamic content of a CGI program is to be sent to standard output.
• A CGI program sends dynamic content to standard output.
• It uses “dup2” function for redirecting standard output to connected descriptor associated with client.
• The result written to standard output by CGI program, it goes directly to client.

Explanation of Solution

Modified C code:

//Define method

void clienterror(int fd, char *cause, char *errnum, char *shortmsg, char *longmsg);

//Define method

void echo(int connfd);

//Define main method

int main(int argc, char **argv)

{

//Declare variables

int listenfd, connfd;

//Call method

Getnameinfo((SA *) &clientaddr, clientlen, hostname, MAXLINE,port, MAXLINE, 0);

//Display message

printf("Accepted connection from (%s, %s)\n", hostname, port);

//Call method

echo(connfd);

//Close

Close(connfd);

}

//Define method

void echo(int connfd)

{

//Declare variable

size_t n;

//Declare array

char buf[MAXLINE];

//Declare variable

rio_t rio;

//Call method

Rio_readinitb(&rio, connfd);

//Loop

while ((n = Rio_readlineb(&rio, buf, MAXLINE)) != 0)

{

//If condition satisfies

if (strcmp(buf, "\r\n") == 0)

//Break

break;

//Call method

Rio_writen(connfd, buf, n);

}

}

Explanation:

• The method “echo” declares the variables first.
• It handles one HTTP response/request transaction.
• The value is been read using method “readinitb” and is stored.
• The value is been written into buffer using “written” method.
• The comparison is made until new line occurs.

B.

Program Plan Intro

IP addresses:

• The IP address denotes an unsigned integer that is 32-bit.
• The IP addresses is been stored by network programs in IP address structure.
• The addresses present in IP address structure are stored in network byte order.
• An unsigned 32-bit integer is converted from host byte order to network byte order by “htonl” function.
• An unsigned 32-bit integer is converted from network byte order host byte order by “ntohl” function.
• The IP address is presented to humans in a form known as “dotted-decimal” notation.
  • Each byte is been represented by its corresponding decimal value and is separated by a period from other bytes.

Passing program arguments to server:

• The arguments for “GET” requests are passed in the URI.
• The character “?” separates filename from the arguments.
• The character “&” separates each argument.
• The arguments do not allow spaces in it.

Server passes arguments to child:

• The server calls “fork” to create a child process and calls “execve” to run program in child’s context once it receives a request.
• The child process sets CGI environment variable values.
• The “adder” program can reference it at run time using “getenv” function of linux.

Output is sent by child:

• The dynamic content of a CGI program is to be sent to standard output.
• A CGI program sends dynamic content to standard output.
• It uses “dup2” function for redirecting standard output to connected descriptor associated with client.
• The result written to standard output by CGI program, it goes directly to client.

Explanation of Solution

Request to TINY for static content:

GET / HTTP/1.1

Host: localhost:5000

User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:53.0) Gecko/20100101 Firefox/53.0

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

Accept-Language: en-US,en;q=0.5

Accept-Encoding: gzip, deflate

Connection: keep-alive

Explanation:

• The given code denotes a request to “TINY” for static content.
• It echoes each and every request line.
• It echoes each and every request header.
• It takes a particular “Accept-Language” and “Accept-Encoding” for the content.

C.

Program Plan Intro

IP addresses:

• The IP address denotes an unsigned integer that is 32-bit.
• The IP addresses is been stored by network programs in IP address structure.
• The addresses present in IP address structure are stored in network byte order.
•  An unsigned 32-bit integer is converted from host byte order to network byte order by “htonl” function.
• An unsigned 32-bit integer is converted from network byte order host byte order by “ntohl” function.
• The IP address is presented to humans in a form known as “dotted-decimal” notation.
  • Each byte is been represented by its corresponding decimal value and is separated by a period from other bytes.

Passing program arguments to server:

• The arguments for “GET” requests are passed in the URI.
• The character “?” separates filename from the arguments.
• The character “&” separates each argument.
• The arguments do not allow spaces in it.

Server passes arguments to child:

• The server calls “fork” to create a child process and calls “execve” to run program in child’s context once it receives a request.
• The child process sets CGI environment variable values.
• The “adder” program can reference it at run time using “getenv” function of linux.

Output is sent by child:

• The dynamic content of a CGI program is to be sent to standard output.
• A CGI program sends dynamic content to standard output.
• It uses “dup2” function for redirecting standard output to connected descriptor associated with client.
• The result written to standard output by CGI program, it goes directly to client.

Explanation of Solution

Version of HTTP:

• The version of HTTP used by browser is HTTP 1.1.
• The output from “TINY” is been inspected for determining HTTP version of browser.
• The “TINY” denotes an iterative server that listens for connection requests on ports.
• The “TINY” executes infinite server loop; it accepts a connection request repeatedly.
• It performs the transaction and closes its end of connection.
• Hence, version of HTTP is “HTTP 1.1”.

D.

Program Plan Intro

IP addresses:

• The IP address denotes an unsigned integer that is 32-bit.
• The IP addresses is been stored by network programs in IP address structure.
• The addresses present in IP address structure are stored in network byte order.
•  An unsigned 32-bit integer is converted from host byte order to network byte order by “htonl” function.
• An unsigned 32-bit integer is converted from network byte order host byte order by “ntohl” function.
• The IP address is presented to humans in a form known as “dotted-decimal” notation.
  • Each byte is been represented by its corresponding decimal value and is separated by a period from other bytes.

Passing program arguments to server:

• The arguments for “GET” requests are passed in the URI.
• The character “?” separates filename from the arguments.
• The character “&” separates each argument.
• The arguments do not allow spaces in it.

Server passes arguments to child:

• The server calls “fork” to create a child process and calls “execve” to run program in child’s context once it receives a request.
• The child process sets CGI environment variable values.
• The “adder” program can reference it at run time using “getenv” function of linux.

Output is sent by child:

• The dynamic content of a CGI program is to be sent to standard output.
• A CGI program sends dynamic content to standard output.
• It uses “dup2” function for redirecting standard output to connected descriptor associated with client.
• The result written to standard output by CGI program, it goes directly to client.

Explanation of Solution

Meaning of HTTP headers:

• The details of each HTTP header is shown below:
  • Accept:14.1:
    • It can be used for specifying certain media types that are acceptable for response.
    • Accept headers are used to indicate that request is limited specifically to a small set of desired types.
    • It has same impact as in case of an in-line image request.
  • Accept-Encoding: 14.3:
    • The request header field is almost similar to “Accept”.
    • It restricts the content-coding that are acceptable in response.
  •  Accept-Language: 14.4:
    • The “Accept-Language” request header is similar to that of “Accept”.
    • It restricts set of natural languages preferred as response to request.
  • Connection: 14.10:
    • The connection header field allows sender to specify options that are desired for particular connection.
    • It must not be communicated by proxies over further connections.
  • Host: 14.23:
    • The host request header field would specify internet host and port number of resource being requested.
    • The host field value denotes origin server’s naming authority or gateway given by original URL.
    • It allows origin server or gateway in differentiating between ambiguous URLs.
    • The root “/” server’s URL is used for multiple host names with single IP address.
  • User-Agent: 14.43:
    • The user-agent request header has information about user agent initiating the request.
    • It is used for tracing protocol violations, automated acknowledgment of user agents for avoiding limitations of user agent.
    • The requests are been added with the field.
    • The field contains multiple product tokens and comments that identifies agent.
    • It includes sub products that forms a significant part of user agent.
    • The product tokens are listed in order of their significance for application identification.