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#include "helpers.h"
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void set_timer_and_handler(void (*handler)(int), long int timer_interval) {
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struct itimerval interval_timer;
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struct sigaction signal_action;
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// Installs handler as the signal handler for SIGALRM
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memset(&signal_action, 0, sizeof(signal_action));
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signal_action.sa_handler = handler;
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if (sigaction(SIGALRM, &signal_action, NULL)) {
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perror("Couldn't install function handler for SIGALRM signals.");
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exit(EXIT_FAILURE);
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}
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// Sets an interval timer to deliver a SIGALRM signal every timer_interval seconds
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interval_timer.it_interval.tv_usec = 0;
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interval_timer.it_interval.tv_sec = timer_interval;
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interval_timer.it_value.tv_usec = 0;
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interval_timer.it_value.tv_sec = timer_interval;
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if (setitimer(ITIMER_REAL, &interval_timer, NULL) == -1) {
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perror("Couldn't set timer.");
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exit(EXIT_FAILURE);
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}
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}
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void enable_echo_broadcast(void) {
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if (system("echo 0 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts") < 0) {
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perror("Couldn't allow echo broadcasts.");
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exit(EXIT_FAILURE);
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}
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}
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/*
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* Function based on this snippet:
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* https://codereview.stackexchange.com/a/58107
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*/
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void search_for_neighbors(node_handle_t **neighbors, uint16_t *num_neighbors, uint16_t port) {
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// Broadcasts ping
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if (system("ping -b 10.255.255.255 -c 3 > /dev/null") < 0) {
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perror("Couldn't broadcast echo.");
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exit(EXIT_FAILURE);
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}
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// Reads the ARP file checking for connected devices
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FILE *arpCache = fopen(ARP_CACHE, "r");
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if (!arpCache) {
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perror("ARP Cache: Failed to open file \"" ARP_CACHE "\"");
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exit(EXIT_FAILURE);
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}
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// Ignores the first line, which contains the header
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char header[ARP_BUFFER_LEN];
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if (!fgets(header, sizeof(header), arpCache)) {
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perror("Couldn't read ARP file header.");
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exit(EXIT_FAILURE);
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}
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// Extracts IP addresses found in the file
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char ipAddr[ARP_BUFFER_LEN];
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char **neighbors_ips = (char **) malloc(sizeof(char *));
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if (!neighbors_ips) {
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perror("Unable to allocate memory for neighbor IP.");
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exit(EXIT_FAILURE);
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}
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int count = 0;
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while (1 == fscanf(arpCache, ARP_LINE_FORMAT, ipAddr)) {
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++count;
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if (count > 1){
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char **r_neighbors_ips = realloc(neighbors_ips, count * sizeof(char *));
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if (!r_neighbors_ips) {
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free(r_neighbors_ips);
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perror("Unable to reallocate memory for neighbor IP.");
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exit(EXIT_FAILURE);
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}
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neighbors_ips = r_neighbors_ips;
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}
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neighbors_ips[count - 1] = (char *) malloc(ARP_BUFFER_LEN * sizeof(char));
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strcpy(neighbors_ips[count - 1], ipAddr);
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}
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// Allocates memory for the new neighbors structs
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if (!(*num_neighbors)) {
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// Neighbors array came empty
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(*neighbors) = (node_handle_t *) malloc(count * sizeof(node_handle_t));
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if (!neighbors_ips) {
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perror("Unable to allocate memory for nodes.");
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exit(EXIT_FAILURE);
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}
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} else {
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node_handle_t *r_neighbors = realloc((*neighbors), count * sizeof(node_handle_t));
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if (!r_neighbors) {
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free(r_neighbors);
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perror("Unable to reallocate memory for nodes.");
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exit(EXIT_FAILURE);
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}
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(*neighbors) = r_neighbors;
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}
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// Adds new event timestamps to neighbors structs
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for (uint8_t i = 0; i < count; ++i) {
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bool found_flag = false;
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for (uint8_t j = 0; j < (*num_neighbors); ++j) {
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if (!strcmp(inet_ntoa(node_get_addr((*neighbors)[j]).sin_addr),
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neighbors_ips[i])) {
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bool node_alive = check_node_alive(neighbors_ips[i]);
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node_add_timestamp((*neighbors)[i], time(NULL), node_alive);
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found_flag = true;
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break;
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}
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}
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if (!found_flag) {
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// New node found!
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printf("Adding %s\n", neighbors_ips[i]);
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struct sockaddr_in peer_name;
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init_sockaddr(&peer_name, neighbors_ips[i], port);
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(*neighbors)[(*num_neighbors)++] = node_init(peer_name);
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}
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}
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if (!((*num_neighbors) == count)) {
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(*num_neighbors) = count;
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}
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fclose(arpCache);
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}
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bool check_node_alive(const char *ipv4) {
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char command[64];
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snprintf(command, 64, "ping %s -c 1 -W 1 | grep \"1 received\" > /dev/null", ipv4);
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int call_res = system(command);
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if (call_res < 0) {
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perror("Couldn't ping node.");
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exit(EXIT_FAILURE);
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}
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return call_res == 0;
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}
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/*
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* Function based on this example:
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* https://www.gnu.org/software/libc/manual/html_node/Inet-Example.html#Inet-Example
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*/
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int create_socket_and_listen(uint16_t port, uint8_t backlog_size) {
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int in_sock;
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struct sockaddr_in own_name;
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// Creates the socket
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in_sock = socket(PF_INET, SOCK_STREAM, 0);
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if (in_sock < 0) {
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perror("Couldn't create the socket.");
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exit(EXIT_FAILURE);
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}
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// Gives the socket a name
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own_name.sin_family = AF_INET;
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own_name.sin_port = htons(port);
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own_name.sin_addr.s_addr = htonl(INADDR_ANY);
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// Binds own address structure to socket
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if (bind(in_sock, (struct sockaddr *) &own_name, sizeof(own_name)) < 0) {
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perror("Couldn't bind the address structure to the socket.");
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exit(EXIT_FAILURE);
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}
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if (listen(in_sock, backlog_size) < 0) {
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perror("Couldn't listen for connections on the socket.");
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exit(EXIT_FAILURE);
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}
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return in_sock;
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}
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void send_message(struct sockaddr_in peer_name, const char *message) {
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int out_sock;
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// Creates the socket
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out_sock = socket(PF_INET, SOCK_STREAM, 0);
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if (out_sock < 0) {
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perror("Couldn't create the socket.");
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exit(EXIT_FAILURE);
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}
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// Connects to the peer
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if (connect(out_sock, (struct sockaddr *) &peer_name, sizeof(peer_name))) {
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printf("Couldn't connect to the peer.\n");
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} else {
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// Sends data to the peer
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write_to_peer(out_sock, message);
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}
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close(out_sock);
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}
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void accept_connection(int sock, struct sockaddr_in *peer_name, fd_set *active_fd_set) {
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size_t peer_name_size = sizeof((*peer_name));
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int comm_socket = accept(sock, (struct sockaddr *) peer_name, &peer_name_size);
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if (comm_socket < 0) {
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perror("Couldn't accept the connection.");
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exit(EXIT_FAILURE);
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}
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fprintf(stderr, "Connected to host %s, port %hd.\n",
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inet_ntoa((*peer_name).sin_addr), ntohs((*peer_name).sin_port));
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FD_SET(comm_socket, active_fd_set);
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}
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void write_to_peer(int file_desc, const char *message) {
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int num_bytes = write(file_desc, message, strlen(message) + 1);
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if (num_bytes < 0) {
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perror("Couldn't write to peer.");
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exit(EXIT_FAILURE);
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}
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}
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int read_from_peer(int file_des, uint16_t max_line) {
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char buffer[max_line];
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int num_bytes;
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num_bytes = read(file_des, buffer, sizeof(buffer));
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if (num_bytes < 0) {
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perror("Couldn't read from peer.");
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exit(EXIT_FAILURE);
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} else if (num_bytes == 0)
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// End-of-file
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return -1;
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else {
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fprintf(stderr, "Got message: `%s'\n", buffer);
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return 0;
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}
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}
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/*
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* Function based on this example:
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* https://www.gnu.org/software/libc/manual/html_node/Inet-Example.html#Inet-Example
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*/
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void init_sockaddr(struct sockaddr_in *peer_name, const char *ipv4, uint16_t port) {
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struct hostent *hostinfo;
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peer_name->sin_family = AF_INET;
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peer_name->sin_port = htons(port);
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hostinfo = gethostbyname(ipv4);
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if (hostinfo == NULL) {
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fprintf(stderr, "Unknown host %s.\n", ipv4);
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exit(EXIT_FAILURE);
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}
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peer_name->sin_addr = *(struct in_addr *) hostinfo->h_addr_list[0];
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}
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