Changed restore connection macro to a function, resolved an internet connection bug and wrote the README.
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lucic71
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# Tema3-Protocoale-de-Comuncatie
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Implemented a web client that communicates witha a REST API. The server basically contains a library where the user
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can store information about books. It supports operations like add_books, delete_books, etc.
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POPESCU LUCIAN IOAN 321CD
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-------------------------
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TEMA 3 PROTOCOALE DE COMUNICATIE
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--------------------------------
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I. File structure
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-----------------
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include/
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authentication.h Contains a auth_info_t object
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book.h Contains a book_info_t object and a book_id_t object
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buffer.h Functions used in connection.c
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cJSON.h JSON parsing library
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commands.h Prototypes of the implemented commands
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connection.h Functions that deal with connection with the server
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dns.h Functions that send DNS requests
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error.h Macros used to print and deal with errors
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http.h Functions that extract info from HTTP headers, etc
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memory.h Macros used for safe memory management(CALLOC, MALLOC, FREE)
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prompt.h Extract data from prompts (for example: username, password)
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requests.h Functions that build GET, POST and DELETE requests
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server.h Information about the server (URLS, NAME, etc)
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./
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authentication.c Implements specific functionality
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book.c Implements specific functionality
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buffer.c Implements specific functionality
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cJSON.c JSON library implementation
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client.c Main driver for client
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commands.c Implements specific functionality
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connection.c Implements specific functionality
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dns.c Implements specific functionality
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http.c Implements specific functionality
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prompt.c Implements specific functionality
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requests.c Implements specific functionality
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Makefile Makefile to build the client
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README This file
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II. Design
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----------
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A. Client and operations(commands)
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----------------------------------
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The implementation of the client is pretty straight forward. The client reads
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input from stdin and using a huge block of if..else statements, it decides which
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operation to make.
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Each operation has three return status codes: OPERATION_SUCCESSFUL,
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OPERATION_CONNECTION_CLOSED and OPERATION_FAILED. The client checks after each
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operation the return code to make sure that the connection with the server is
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still ok, if not it retries to re-establish it. It also checks that the
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operations were successful in order to manage the correct creation and deletion
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of cookies and JWT tokens.
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The operations are implemented using the same rules:
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- fetch data from user if needed
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- build the HTTP request
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- send the request and receive the response
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- work with the response if needed
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Moreover each operation takes care of the errors which may occur during the
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above mentioned steps. For this each variable is declared at the beginning
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of each opearion and if an error occurs the memory will be free'd for this
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variables using a goto statement and a label at the end of the current
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operation.
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B. JSON
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-------
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For parsing, converting and working with JSON objects I used the cJSON library.
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It is a simple library containing only a header file and a source file, that
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can easily be inserted in the project.
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I chose this library because it has a basic interface containing functions and
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objects that require a small amount of time to understand, as the authors say:
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"cJSON aims to be the dumbest possible parser that you can get your job done
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with".
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More info and tutorials can be found on their github page:
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"https://github.com/DaveGamble/cJSON".
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C. Reading data from user
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-------------------------
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prompt.c is the file where this functionality is implemented. It pops up a
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prompt for the required data and using a basic read function like fgets it
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gets the job done. I also added password safety by turning off the echoing
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when the password is inserted.
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D. Other objects and functionality
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----------------------------------
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For keeping all as simple as possible, I encapsulated the information coming
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from the user (username, password, book info) in objects that have their own
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metods for parsing to JSON or deletion. Their location can be found in
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I. File structure.
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The functionality for connecting with the server and creating requests is
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mainly borrowed from lab10 HTTP with some minor changes.
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It uses cookies to store a session and JWT tokens to restrict user access into the library.
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The communication with the server is over the HTTP protocol, using GET POST and DELETE requests.
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It uses cJSON library to work with JSON objects.
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@ -61,8 +61,3 @@ void delete_auth_info(auth_info_t *auth_info) {
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FREE(auth_info);
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}
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@ -10,21 +10,6 @@
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#include "memory.h"
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#include "commands.h"
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/*
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* This macro makes a stable connection with the server.
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*
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*/
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#define RESTORE_SOCKFD(assertion, sockfd, server_ip) \
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do { \
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if (assertion) { \
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ERROR(SERVER_CONNECTION_CLOSED); \
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sockfd = -1; \
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while (sockfd < 0) { \
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sockfd = open_connection(server_ip, PORT, AF_INET, SOCK_STREAM, 0); \
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} \
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} \
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} while (sockfd < 0)
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int main() {
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/*
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@ -77,30 +62,38 @@ int main() {
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memset(input_buffer, 0x00, MAX_COMMAND_SZ);
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fgets(input_buffer, MAX_COMMAND_SZ - 1, stdin);
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/*
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* Possible values:
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*
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* OPERATION_SUCCESSFUL
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* OPERATION_FAILED
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* OPERATION_CONNECTION_CLOSED
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*
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*/
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int operation_status;
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if (strncmp(input_buffer, REGISTER, sizeof(REGISTER) - 1) == 0) {
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int register_ret = op_register(&sockfd);
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operation_status = op_register(&sockfd);
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/*
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* If the connection closed during the register operation then a new
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* socket must be opened for the communication with the server.
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*
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*/
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RESTORE_SOCKFD(register_ret == OPERATION_CONNECTION_CLOSED,
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sockfd, server_ip);
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if (operation_status == OPERATION_CONNECTION_CLOSED) {
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restore_connection(&sockfd, server_ip);
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}
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} else if (strncmp(input_buffer, LOGIN, sizeof(LOGIN) - 1) == 0) {
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int login_ret = login(&sockfd, &cookie);
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RESTORE_SOCKFD(login_ret == OPERATION_CONNECTION_CLOSED,
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sockfd, server_ip);
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operation_status = login(&sockfd, &cookie);
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if (operation_status == OPERATION_CONNECTION_CLOSED) {
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restore_connection(&sockfd, server_ip);
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}
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/*
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* If the login was successful then the client must delete the previous
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* @jwt_token.
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*
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*/
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if (login_ret == OPERATION_SUCCESSFUL) {
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if (operation_status == OPERATION_SUCCESSFUL) {
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FREE(jwt_token);
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}
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@ -111,52 +104,64 @@ int main() {
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* delete it because a new enter_library will generate a new jwt_token.
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*
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*/
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int enter_library_ret = enter_library(&sockfd, cookie, &jwt_token);
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RESTORE_SOCKFD(enter_library_ret == OPERATION_CONNECTION_CLOSED,
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sockfd, server_ip);
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operation_status = enter_library(&sockfd, cookie, &jwt_token);
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if (operation_status == OPERATION_CONNECTION_CLOSED) {
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restore_connection(&sockfd, server_ip);
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}
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} else if (strncmp(input_buffer, GET_BOOKS, sizeof(GET_BOOKS) - 1) == 0) {
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int get_books_ret = get_books(&sockfd, jwt_token);
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RESTORE_SOCKFD(get_books_ret == OPERATION_CONNECTION_CLOSED,
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sockfd, server_ip);
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operation_status = get_books(&sockfd, jwt_token);
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if (operation_status == OPERATION_CONNECTION_CLOSED) {
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restore_connection(&sockfd, server_ip);
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}
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} else if (strncmp(input_buffer, GET_BOOK, sizeof(GET_BOOK) - 1) == 0) {
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int get_book_ret = get_book(&sockfd, jwt_token);
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RESTORE_SOCKFD(get_book_ret == OPERATION_CONNECTION_CLOSED,
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sockfd, server_ip);
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operation_status = get_book(&sockfd, jwt_token);
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if (operation_status == OPERATION_CONNECTION_CLOSED) {
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restore_connection(&sockfd, server_ip);
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}
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} else if (strncmp(input_buffer, ADD_BOOK, sizeof(ADD_BOOK) - 1) == 0) {
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int add_book_ret = add_book(&sockfd, jwt_token);
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RESTORE_SOCKFD(add_book_ret == OPERATION_CONNECTION_CLOSED,
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sockfd, server_ip);
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operation_status = add_book(&sockfd, jwt_token);
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if (operation_status == OPERATION_CONNECTION_CLOSED) {
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restore_connection(&sockfd, server_ip);
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}
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} else if (strncmp(input_buffer, DELETE_BOOK, sizeof(DELETE_BOOK) - 1) == 0) {
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int delete_book_ret = delete_book(&sockfd, jwt_token);
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RESTORE_SOCKFD(delete_book_ret == OPERATION_CONNECTION_CLOSED,
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sockfd, server_ip);
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operation_status = delete_book(&sockfd, jwt_token);
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if (operation_status == OPERATION_CONNECTION_CLOSED) {
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restore_connection(&sockfd, server_ip);
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}
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} else if (strncmp(input_buffer, LOGOUT, sizeof(LOGOUT) - 1) == 0) {
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int logout_ret = logout(&sockfd, cookie);
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RESTORE_SOCKFD(logout_ret == OPERATION_CONNECTION_CLOSED,
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sockfd, server_ip);
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operation_status = logout(&sockfd, cookie);
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if (operation_status == OPERATION_CONNECTION_CLOSED) {
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restore_connection(&sockfd, server_ip);
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}
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/*
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* Delete the cookie and the jwt_token if the operation was successful.
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*
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*/
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if (logout_ret == OPERATION_SUCCESSFUL) {
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if (operation_status == OPERATION_SUCCESSFUL) {
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FREE(cookie);
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FREE(jwt_token);
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}
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} else if (strncmp(input_buffer, EXIT, sizeof(EXIT) - 1) == 0) {
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puts("Closing the connection with the server, goodbye.");
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puts(GOODBYE);
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close(sockfd);
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FREE(cookie);
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@ -148,6 +148,19 @@ char *receive_from_server(int sockfd) {
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int send_and_receive(int *sockfd, char *request, char **response) {
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char *server_ip = get_ip(SERVER);
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/*
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* If the internet connection dies while the client runs, get_ip will
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* detect this because it makes a DNS request that will use the connection.
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*
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* So the client will die to.
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*
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*/
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if (server_ip == NULL) {
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ERROR(NO_INTERNET_CONNECTION);
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exit(EXIT_FAILURE);
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}
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bool connection_failed = false;
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int return_status = SEND_RECV_FAIL;
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@ -200,3 +213,19 @@ int send_and_receive(int *sockfd, char *request, char **response) {
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return return_status;
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}
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void restore_connection(int *sockfd, char *server_ip) {
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for (size_t i = 0; i < SEND_RECV_TIMEOUT; i++) {
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*sockfd = open_connection(server_ip, PORT, AF_INET, SOCK_STREAM, 0);
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if (*sockfd > 0) {
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return;
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}
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}
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ERROR(UNSTABLE_INTERNET_CONNECTION);
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exit(EXIT_FAILURE);
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}
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@ -64,4 +64,11 @@ char *receive_from_server(int sockfd);
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int send_and_receive(int *sockfd, char *request, char **response);
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/*
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* Make a stabile connection with the server.
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*
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*/
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void restore_connection(int *sockfd, char *server_ip);
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#endif
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@ -63,8 +63,9 @@
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* Error messages for connection with the server.
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*
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*/
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#define SERVER_CONNECTION_CLOSED "Server closed the connection. Please retry the operation!"
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#define NO_INTERNET_CONNECTION "There is no internet connection!"
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#define SERVER_CONNECTION_CLOSED "Server closed the connection. Please retry the operation!"
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#define NO_INTERNET_CONNECTION "There is no internet connection!"
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#define UNSTABLE_INTERNET_CONNECTION "Unstable internet connection! Please retry."
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/*
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* Error messages for invalid cookies or tokens.
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#define JWT_TOKEN_ERROR "You must enter library before making this operation!"
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#define ENTER_LIBARY_ERROR "You are already in library!"
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/*
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* Status message for closing the client.
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*
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*/
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#define GOODBYE "Closing the connection with the server, goodbye."
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#define ERROR_HANDLER(assertion, return_value) \
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do { \
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if (assertion) { \
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