Only Listens

README.md

 # Simple Chat Server
 
 This is a simple chat server that broadcasts messages to all users.
+
+### References
+
+- [Beej's Socket Programming Guide](https://beej.us/guide/bgnet/pdf/bgnet_usl_c_1.pdf)

server.c

+/*
+** pollserver.c -- a cheezy multiperson chat server
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+#include <poll.h>
+
+#define PORT "9034" // Port we're listening on
+
+// Get sockaddr, IPv4 or IPv6:
+void *get_in_addr(struct sockaddr *sa)
+{
+if (sa->sa_family == AF_INET) {
+return &(((struct sockaddr_in*)sa)->sin_addr);
+}
+
+return &(((struct sockaddr_in6*)sa)->sin6_addr);
+}
+
+// Return a listening socket
+int get_listener_socket(void)
+{
+int listener; // Listening socket descriptor
+int yes=1; // For setsockopt() SO_REUSEADDR, below
+int rv;
+
+struct addrinfo hints, *ai, *p;
+
+// Get us a socket and bind it
+memset(&hints, 0, sizeof hints);
+hints.ai_family = AF_UNSPEC;
+hints.ai_socktype = SOCK_STREAM;
+hints.ai_flags = AI_PASSIVE;
+if ((rv = getaddrinfo(NULL, PORT, &hints, &ai)) != 0) {
+
+fprintf(stderr, "selectserver: %s\n", gai_strerror(rv));
+exit(1);
+}
+
+for(p = ai; p != NULL; p = p->ai_next) {
+listener = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
+if (listener < 0) {
+continue;
+}
+
+// Lose the pesky "address already in use" error message
+setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int));
+
+if (bind(listener, p->ai_addr, p->ai_addrlen) < 0) {
+close(listener);
+continue;
+}
+
+break;
+}
+
+freeaddrinfo(ai); // All done with this
+
+// If we got here, it means we didn't get bound
+if (p == NULL) {
+return -1;
+}
+
+// Listen
+if (listen(listener, 10) == -1) {
+return -1;
+}
+
+return listener;
+}
+
+// Add a new file descriptor to the set
+void add_to_pfds(struct pollfd *pfds[], int newfd, int *fd_count, int *fd_size)
+{
+// If we don't have room, add more space in the pfds array
+if (*fd_count == *fd_size) {
+*fd_size *= 2; // Double it
+
+*pfds = realloc(*pfds, sizeof(**pfds) * (*fd_size));
+}
+
+(*pfds)[*fd_count].fd = newfd;
+(*pfds)[*fd_count].events = POLLIN; // Check ready-to-read
+
+(*fd_count)++;
+}
+
+// Remove an index from the set
+void del_from_pfds(struct pollfd pfds[], int i, int *fd_count)
+{
+// Copy the one from the end over this one
+pfds[i] = pfds[*fd_count-1];
+
+ (*fd_count)--;
+ }
+
+ // Main
+ int main(void)
+ {
+ int listener; // Listening socket descriptor
+
+ int newfd; // Newly accept()ed socket descriptor
+ struct sockaddr_storage remoteaddr; // Client address
+ socklen_t addrlen;
+
+ char buf[256]; // Buffer for client data
+
+ char remoteIP[INET6_ADDRSTRLEN];
+
+ // Start off with room for 5 connections
+ // (We'll realloc as necessary)
+ int fd_count = 0;
+ int fd_size = 5;
+ struct pollfd *pfds = malloc(sizeof *pfds * fd_size);
+
+ // Set up and get a listening socket
+ listener = get_listener_socket();
+
+ if (listener == -1) {
+ fprintf(stderr, "error getting listening socket\n");
+ exit(1);
+ }
+
+ // Add the listener to set
+ pfds[0].fd = listener;
+ pfds[0].events = POLLIN; // Report ready to read on incoming connection
+
+ fd_count = 1; // For the listener
+
+ // Main loop
+ for(;;) {
+ int poll_count = poll(pfds, fd_count, -1);
+
+ if (poll_count == -1) {
+ perror("poll");
+ exit(1);
+ }
+
+ // Run through the existing connections looking for data to read
+ for(int i = 0; i < fd_count; i++) {
+
+ // Check if someone's ready to read
+ if (pfds[i].revents & POLLIN) { // We got one!!
+
+ if (pfds[i].fd == listener) {
+ // If listener is ready to read, handle new connection
+
+ addrlen = sizeof remoteaddr;
+ newfd = accept(listener,
+ (struct sockaddr *)&remoteaddr,
+ &addrlen);
+
+ if (newfd == -1) {
+ perror("accept");
+ } else {
+ add_to_pfds(&pfds, newfd, &fd_count, &fd_size);
+
+ printf("pollserver: new connection from %s on "
+ "socket %d\n",
+ inet_ntop(remoteaddr.ss_family,
+ get_in_addr((struct sockaddr*)&remoteaddr),
+ remoteIP, INET6_ADDRSTRLEN),
+ newfd);
+ }
+ } else {
+ // If not the listener, we're just a regular client
+ int nbytes = recv(pfds[i].fd, buf, sizeof buf, 0);
+
+ int sender_fd = pfds[i].fd;
+
+ if (nbytes <= 0) {
+ // Got error or connection closed by client
+ if (nbytes == 0) {
+ // Connection closed
+ printf("pollserver: socket %d hung up\n", sender_fd);
+ } else {
+ perror("recv");
+ }
+
+ close(pfds[i].fd); // Bye!
+
+ del_from_pfds(pfds, i, &fd_count);
+
+ } else {
+ // We got some good data from a client
+ 
+ }
+ } // END handle data from client
+ } // END got ready-to-read from poll()
+ } // END looping through file descriptors
+ } // END for(;;)--and you thought it would never end!
+
+ return 0;
+ }