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https://github.com/hakimkartik/course-registration

A TCP/UDP backend server to handle student course registration, written in C
https://github.com/hakimkartik/course-registration

c cli tcp-client tcp-server terminal-based udp-server

Last synced: 3 months ago
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A TCP/UDP backend server to handle student course registration, written in C

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README 

          




  

  

  readme

  



  


EE450 Project




				Name: Kartik Hakim



				USC ID: 9520-8829-28



				Extra Credit Section : Done





Project flow chart:


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tcpServerPort:25928
udpClientPort:24928
udpServerPort:21928
udpServerPort:23928
udpServerPor:22928
client
serverM
serverC
serverCS
serverEE


What have I done in this assignment?


In this socket-programming project using CPP language, I implemented the simulation of a web registration process.


In this process, a client will enter the course code and category of the information he/she wishes to retrieve.


This client will communicate with serverM process, which in turn will communicate with credential (serverC) and backend servers (serverEE, serverCS) .


I tested all code both on my local Mac (M2 chip) and studentVM (ubuntu 16).


Comments




Idiosyncrasies of the project




Please keep following suggestions in mind while testing:


    

  1. 

    Please prefer reading from readme.html.
    

    2. 

  2. 

    If while testing client is stopped or gets stuck, please restart all processes, it should start working fine.
    

    3. 

  3. 

    Please make sure course-ids are inputted in the syntax mentioned in How to run the programs section
    

    4. 

  4. 

    If while testing, authentication is failing, please restart client, serverM and serverC.
    

    5. 

  5. 

    If serverM exits with following error
    

    6. 





libc++abi: terminating with uncaught exception of type std::out_of_range: basic_string



zsh: abort ./serverM





Please restart  client , serverCand serverM processes.


    

  1. Sometimes the I/O  buffers will not read properly, so the messages will not be printed properly on the console.
    2. 



james sent a request to the main server.

The client received the response from the Main server using TCP over port 52446.

.he CourseName of EE450 is Introduction to Computer Networks



The ServerEE received a request from the Main Server about the CourseName of EE450.

The course information has been found: The CourseName of EE450 is Introduction to . mputer Networks

The ServerEE finished sending the response to the Main Server.



It should get fixed by restarting all 5 processes.


How to run the programs


Please start the 5 processes in following format:-


    

  1. 

    First open 5 different terminal window instances.
    

    2. 

  2. 

    Use one terminal and type make all to compile all the cpp files.
    

    3. 





ee450_hakim_kartik_9520882928 % make all



g++ -std=c++11 -shared-libgcc serverM.cpp -o serverM



g++ -std=c++11 -shared-libgcc serverC.cpp -o serverC



g++ -std=c++11 -shared-libgcc serverEE.cpp -o serverEE



g++ -std=c++11 -shared-libgcc serverCS.cpp -o serverCS



g++ -std=c++11 -shared-libgcc client.cpp -o client



ee450_hakim_kartik_9520882928 %





    

  1. Start the processes in following order
    2. 






Terminal 1: ./serverEE


Terminal 2: ./serverCS


Terminal 3: ./serverC


Terminal 4: ./serverM


Terminal 5: ./client


    

  1. Input syntax in terminal 1, for client process:
    2. 



    

  • While entering username and password:
    • 





ee450_hakim_kartik_9520882928 % ./client



The client is up and running.



  



Please enter the username: james



Please enter the password: Th!r3oe4s



james sent an authentication request to the main server.



james received the result of authentication using TCP over port 51750. Authentication failed: Password does not match.



Attempts remaining: 2



  



Please enter the username: amber



Please enter the password: cOntra4@positiv1e



amber sent an authentication request to the main server.



amber received the result of authentication using TCP over port 51759. Authentication failed: Password does not match.



Attempts remaining: 1



  



Please enter the username: james



Please enter the password: 2kAnsa7s)



james sent an authentication request to the main server.



james received the result of authentication using TCP over port 51767. Authentication is successful





    

  • While entering single course-ids
    • 





Please enter the course code to query: EE450



Please enter the category(Credit / Professor / Days / CourseName): Days



james sent a request to the main server.



The client received the response from the Main server using TCP over port 51767.



The Days of EE450 is Tue;Thu





    

  • While entering multiple course-ids
    • 





Please enter the course code to query: EE450 CS100 EE520



james sent a request to the main server.



The client received the response from the Main server using TCP over port 52001.



CourseCode: Credits, Professor, Days, Course Name



EE450: 4,Ali Zahid,Tue;Thu,Introduction to Computer Networks



CS100: 4,Sathyanaraya Raghavachary,Tue;Thu,Explorations in Computing



EE520: 4,Todd Brun,Tue;Thu,Introduction to Quantum Information Processing





Incorrect way of input


    

  • 

    DO NOT ENTER UNEXPECTED SPACES
    

    • 

  • 

    END ALL LINES USING NEWLINE CHARACTERS
    

    • 





Please enter the course code to query: EE450 CS100



EE520



james sent a request to the main server.



The client received the response from the Main server using TCP over port 52029.



CourseCode: Credits, Professor, Days, Course Name



EE450: 4,Ali Zahid,Tue;Thu,Introduction to Computer Networks



CS100: 4,Sathyanaraya Raghavachary,Tue;Thu,Explorations in Computing



EE520: 4,Todd Brun,Tue;Thu,Introduction to Quantum Information Processing







Please enter the course code to query: EE450



  

  

  

  

  

  



EE520



james sent a request to the main server.



The client received the response from the Main server using TCP over port 52030.



CourseCode: Credits, Professor, Days, Course Name



EE450: 4,Ali Zahid,Tue;Thu,Introduction to Computer Networks



EE520: 4,Todd Brun,Tue;Thu,Introduction to Quantum Information Processing



  



-----Start a new request-----



  



Please enter the course code to query:





Implementations




What your code files are and what each one of them does




client


The workflow of client is as follows:


    

  1. 

    client process start a TCP socket and uses a dynamically assigned port number.
    

    2. 

  2. 

    Enter the username and password.
    

    3. 

  3. 

    The given username and password (say u1,p1), are appended in a string template username:<u1>,password:<p1>.
    

    4. 

  4. 

    This template is sent via TCP to serverM.
    

    5. 

  5. 

    The serverM checks with serverC and responds, via TCP, one of the following strings as response:
    

    *  Username not found
    

    *  Username found, Password didnt match
    

    * Username verified
    

    * Not sure
    

    6. 

  6. 

    If the response is Username verified, client will expect to read course and category and code will move to steps 7-10.
    

    7. 



If the response is not Username verified, steps 1-6 will be repeated.


    

  1. 

    User will enter course code and category(expected values are Credit / Professor / Days / CourseName ), say c1 and c2.
    

    2. 

  2. 

    Will create a string template course:<c1>,category:<c2> and send to serverM via TCP.
    

    3. 

  3. 

    serverM will check with respective backend servers, via UDP, and responds either with the requested information (if the course-code is present in DB) or with string NO_DATA (if the course-code is not present in DB).
    

    4. 

  4. 

    client will process the response from serverM, via TCP, and print appropriate messages on the console.
    

    5. 





serverM


The workflow of serverMis as follows:


    

  1. 

    serverM expects to receive a string template of format username:<u1>,password:<p1> from client via TCP over port 25928.
    

    2. 

  2. 

    serverM extracts the username, u1 and password, p1 from the template and encrypts them.
    

    3. 

  3. 

    The encrypted username and password, say e1 and e2, are sent to serverC via UDP over port 24928.
    

    4. 

  4. 

    serverC replies, via UDP, with one of the following strings:
    

    *  Username not found
    

    *  Username found, Password didnt match
    

    * Username verified
    

    * Not sure
    

    5. 

  5. 

    serverM forwards these response from serverC to client, via TCP.
    

    6. 

  6. 

    If the serverC, response is Username verified, a flag is set, to expect course-category string template, from client.
    

    7. 

  7. 

    Once the flag is set, serverM receives client-category template from client.
    

    8. 

  8. 

    serverM will extract course and category, say c1 and c2, and based on the first 2 characters of course c1 will choose appropriate backend servers.
    

    9. 

  9. 

    serverM will send the string template course:<c1>,category:<c2> to backend servers (serverCS or serverEE) via UDP over port, 24928.
    

    10. 

  10. 

    Once serverM receives the response, it forwards it to client, via TCP over port 25928.
    

    11. 





serverC


The workflow of serverC is as follows:


    

  1. 

    serverC expects a string containing u1,p1 via UDP over port 21928.
    

    2. 

  2. 

    serverC reads the txt file cred.txt and stores in a global map variable.
    

    3. 

  3. 

    Once we receive the string, we extract u1 and p1 and look for u1 as a key in the global map.
    

    4. 

  4. 

    If u1 is found in the map, we check p1 is similar to password stored in map.
    

    5. 

  5. 

    Based on both the comparison, a string response is selected:
    

    *  Username not found
    

    *  Username found, Password didnt match
    

    * Username verified
    

    * Not sure
    

    6. 

  6. 

    This string response is replied back to serverM.
    

    7. 





serverCS/EE


The workflow of backend servers (serverEE/serverCS) is as follows:


    

  1. 

    serverEE/CS expects a string containing course:<c1>,category:<c2> via UDP over port 23928(serverEE) or port 22928(serverCS) from serverM.
    

    2. 

  2. 

    serverEE/CS reads the txt file ee.txt (serverEE) or cs.txt (serverCS) and stores in 4 global map variables (credit / professor name/ course name / credits).
    

    3. 

  3. 

    Once we receive the string, we extract course id, c1, and course category, c2.
    

    4. 

  4. 

    Based on c2, category, we select the appropriate map variable, search for course id c1, and store the response as string.
    

    5. 

  5. 

    If course code is not found, we set the response to NOT_FOUND.
    

    6. 

  6. 

    We reply back the response to serverM.
    

    7. 

  7. 

    For extra credit section, I set category to everything and read information from all 4 global variable maps and append them in the response variable .
    

    8. 



Message Formats



code

UserName / Password

CourseCategory



client

username:u1,password:p1

course:c1,category:c2



serverM

username:eU1,password:eP1

course:c1,category:c2



serverC

username:eU1,password:eP1

NA



serverCS

NA

c1,c2



serverEE

NA

c1,c2



where:


u1 : username entered on client terminal


p1 : password enter on client terminal


eU1: encrypted username sent by serverM to serverC


eP1 : encrypted password sent by serverM to serverC


c1 : course id entered on client terminal sent by client to serverM to backend servers


c2 : course category entered on client terminal by client to serverM to backend servers


Reused Code




For example



from section 6.5:-




int sockfd, rv, numbytes;



  



struct addrinfo hints, *servinfo, *p;



  



struct sockaddr_storage their_addr;



  



  



socklen_t addr_len;



  



char s[INET6_ADDRSTRLEN];



  



memset(&hints, 0, sizeof hints);



  



hints.ai_family = AF_INET6;



  



hints.ai_socktype = SOCK_DGRAM;



  



//hints.ai_flags = AI_PASSIVE; // use my IP



  



hints.ai_flags = INADDR_ANY; // using localhost as IP



  



if ((rv = getaddrinfo(NULL, MY_UDP_PORT, &hints, &servinfo)) != 0)



  



{



  



fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));



  



exit(2);



  



}



  



  



// loop through all the results and bind to the first we can



  



for (p = servinfo; p != NULL; p = p->ai_next)



  



{



  



if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1)



  



{



  



perror("serverEE : socket");



  



continue;



  



}



  



  



if (::bind(sockfd, p->ai_addr, p->ai_addrlen) == -1)



  



{



  



close(sockfd);



  



perror("bind failed in serverEE, will try another socket");



  



continue;



  



}



  



  



break;



  



}



  



  



if (p == NULL)



  



{



  



fprintf(stderr, "bind failed in serverEE\n");



  



exit(2);



  



}



  



  



freeaddrinfo(servinfo);







For example:-




read(newsockfd,buffer,255)







if (connect(sockfd,&serv_addr,sizeof(serv_addr)) < 0)



error("ERROR connecting");









int sockfd = socket(domain, type, protocol) ;



  



int bind(int sockfd, const struct sockaddr *addr, socklen_t addrlen) ;



  



int new_socket= accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);









vector<string> result;



  



stringstream s_stream(my_str); //create string stream from the string



while (s_stream.good())



  



{



string substr;



getline(s_stream, substr, ','); //get first string delimited by comma



result.push_back(substr);



}



  









void ltrim(string &s) {



  



s.erase(s.begin(), find_if(s.begin(), s.end(), [](unsigned char ch) {



  



return !std::isspace(ch);



  



}));



  



}



  



  



// trim from end (in place)



  



void rtrim(string &s) {



  



s.erase(find_if(s.rbegin(), s.rend(), [](unsigned char ch) {



  



return !std::isspace(ch);



  



}).base(), s.end());



  



}



  



  



// trim from both ends (in place)



  



void trim(string &s) {



  



ltrim(s);



  



rtrim(s);



  



}





Extra files


    

  • 

    stringUtil.h : custom header file having string trimming code for given input string.
    

    • 

  • 

    codec.h : custom header having encryption / decryption code for credential verification.
    

    •