Concept explainers
A.
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
- 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.
A.
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.
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.
B.
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.
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.
C.
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.
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.
D.
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.
- Accept:14.1:
Want to see more full solutions like this?
Chapter 11 Solutions
Computer Systems: A Programmer's Perspective (3rd Edition)
- Using the domain name www.practice.com, construct the URL for a file called overview.html in a folder called video, which is in a folder called Resources, which is in the web root directory. Do NOT include a protocol (e.g. http:// or https://). Please note that case does matter for many servers, but the Canvas quiz tool cannot check for case. For example, history.html and History.html are NOT the same, but Canvas cannot discern the difference, so be careful to match the case exactly for file and folder names.arrow_forwardIn this assignment, you will develop a simple Web server in Python that is capable of processing only one request. Specifically, your Web server will (i) Create a connection socket when contacted by a client (browser) (ii) Receive the HTTP request from this connection(iii) Parse the request to determine the specific file being requested(iv) Get the requested file from the server’s file system(v) Create an HTTP response message consisting of the requested file preceded by header lines(vi) Send the response over the TCP connection to the requesting browser. If a browser requests a file that is not present in your server, your server should return a “404 Not Found” error message. Your job is to code the steps above, run your server, and then test your server by sending requests from browsers running on different hosts. If you run your server on a host that already has a Web server running on it, then you should use a different port than port 80 for your Web server. Make sure to test your…arrow_forwardn this assignment, you will develop a simple Web server in Python that is capableof processing only one request. Specifically, your Web server will(i) Create a connection socket when contacted by a client (browser)(ii) Receive the HTTP request from this connection(iii) Parse the request to determine the specific file being requested(iv) Get the requested file from the server’s file system(v) Create an HTTP response message consisting of the requested filepreceded by header lines(vi) Send the response over the TCP connection to the requesting browser.If a browser requests a file that is not present in your server, your server shouldreturn a “404 Not Found” error message.Your job is to code the steps above, run your server, and then test your server bysending requests from browsers running on different hosts. If you run your serveron a host that already has a Web server running on it, then you should use a differentport than port 80 for your Web server. Make sure to test your program…arrow_forward
- Consider the following string of ASCII characters that were captured by Wireshark when the browser sent an HTTP GET message (i.e., this is the actual content of an HTTP GET message). The characters <cr><lf> are carriage return and line-feed characters (that is, the italized character string <cr> in the text below represents the single carriage-return character that was contained at that point in the HTTP header). Answer the following questions, indicating where in the HTTP GET message below you will find the answer.arrow_forwardExamine this HTTP header snippet (highlighted in blue, this is the first few bytes of the full HTTP header). The first 8 bytes of the HTTP Header are 48 54 54 50 2f 31 2e 31. What are the ASCII characters corresponding to these hex characters (use an online ASCII table, if needed).arrow_forwardIN PHP please help with the following: True or false Form data submitted with the HTTP POST method is displayed in the browser URL. In PHP, strings can be delimited either by single straight quotes or by apostrophes. PHP can only include files that have the ".php" extension. SESSION identifiers are shared among different users on the same script.arrow_forward
- Q2: A browser asks for the web page: www.google.com/sites.html. The web server responds with status that the requested page does not found. Write the exact format for the HTTP 1.0 request message and the response message. Include the necessary headers (if exists).arrow_forwardThe If-Modified-Since header can be used to check whether a cached page is still valid. Requests can be made for pages containing images, sound, video, and so on, as well as HTML. Do you think the effectiveness of this technique is better or worse for JPEG images as compared to HTML? Think carefully about what "effectiveness" means and explain your answer.arrow_forwardGet and Post are wo different methods of HTTP in which information such as parameters of a form element can be sent from a browser to a web server. List three differences between two methods in a browser behavior when sending the information in those two methods. Write the answer in three comparisons in a, b, c as Get: a, b, c. POST: a, b, c.arrow_forward
- In this part, we add the CPU temperature ID of the Raspberry Pi to the MQTT stream. Open a new terminal and create a new script by the name of py and add the following content to it. import paho.mqtt.client as mqtt import time from subprocess import check_output from re import findall def get_temp(): temp = check_output(["vcgencmd","measure_temp"]).decode("UTF-8") return(findall("\d+\.\d+",temp)[0]) def on_connect(client, userdata, flags, rc): print("Connected with result code "+str(rc)) client.subscribe("etec224_mqtt_test/") global Connected Connected = True Connected = False client = mqtt.Client() client.on_connect = on_connect client.connect("broker.emqx.io", 1883, 60) client.loop_start() while Connected!= True: #Wait Here time.sleep(0.1) try: while True: value = get_temp() client.publish('etec224_mqtt_test/', value) time.sleep(1) except KeyboardInterrupt: client.disconnect()…arrow_forward2. Write the complete link for the get request of an API using the information given below. Base address: https://api.openweathermap.org/data/2.5/weather Key Value appid c825d459c172fk1fcbd5932k117Is6a917 city London units metric mode xmlarrow_forwardYou are required to access any 5 HTTP objects (among them at least one should be an html, image, video and pdf objects). You are required to capture the HTTP request messages and their corresponding HTTP response messages through Wireshark or any other sniffing tool. With reference to corresponding HTTP RFCs, explain each header line of both the HTTP request and response messages.arrow_forward
- Database System ConceptsComputer ScienceISBN:9780078022159Author:Abraham Silberschatz Professor, Henry F. Korth, S. SudarshanPublisher:McGraw-Hill EducationStarting Out with Python (4th Edition)Computer ScienceISBN:9780134444321Author:Tony GaddisPublisher:PEARSONDigital Fundamentals (11th Edition)Computer ScienceISBN:9780132737968Author:Thomas L. FloydPublisher:PEARSON
- C How to Program (8th Edition)Computer ScienceISBN:9780133976892Author:Paul J. Deitel, Harvey DeitelPublisher:PEARSONDatabase Systems: Design, Implementation, & Manag...Computer ScienceISBN:9781337627900Author:Carlos Coronel, Steven MorrisPublisher:Cengage LearningProgrammable Logic ControllersComputer ScienceISBN:9780073373843Author:Frank D. PetruzellaPublisher:McGraw-Hill Education