a simple server framework in Linux C

server framework in Linux C"/>

a simple server framework in Linux C

以前学习整理的demo：

/** daemon.c** Copyright 2012 vince <vince@vince-vsing>** This program is free software; you can redistribute it and/or modify* it under the terms of the GNU General Public License as published by* the Free Software Foundation; either version 2 of the License, or* (at your option) any later version.** This program is distributed in the hope that it will be useful,* but WITHOUT ANY WARRANTY; without even the implied warranty of* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the* GNU General Public License for more details.** You should have received a copy of the GNU General Public License* along with this program; if not, write to the Free Software* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,* MA 02110-1301, USA.***/#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <ctype.h>#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>#include <errno.h>
#include <syslog.h>
#include <libgen.h>#define DEV_NULL "/dev/null"
#define ROOT_PATH     "/"void daemon_handle_connection(int fd) {
/*child process do something here*/
}int redirect_fd(int fd, int flags) {/* Attempt to open bit bucket */int new_fd = open(DEV_NULL, flags);if (new_fd < 0)return 1;/* If descriptor is different, redirect old to new and close new */if (new_fd != fd) {dup2(new_fd, fd);close(new_fd);}return 0;}int daemonize() {pid_t pid;/* Fork once to ensure we aren't the process group leader */pid = fork();if (pid < 0) {printf("Could not fork() parent: %s", strerror(errno));return 1;}/* Exit if we are the parent */if (pid > 0) {printf("Exiting and passing control to PID %i", pid);_exit(0);}/* Start a new session (if not already group leader) */setsid();/* Fork again so the session group leader exits */pid = fork();if (pid < 0) {printf("Could not fork() group leader: %s", strerror(errno));return 1;}/* Exit if we are the parent */if (pid > 0) {printf("Exiting and passing control to PID %i", pid);_exit(0);}/* Change to root directory */if (chdir(ROOT_PATH) < 0) {printf("Unable to change working directory to "ROOT_PATH);return 1;}/* Reopen the 3 stdxxx to /dev/null */if (redirect_fd(STDIN_FILENO, O_RDONLY)|| redirect_fd(STDOUT_FILENO, O_WRONLY)|| redirect_fd(STDERR_FILENO, O_WRONLY)) {printf("Unable to redirect standard file descriptors to "DEV_NULL);return 1;}/* Success */return 0;}int main(int argc, char* argv[]) {/* Server */int socket_fd;struct addrinfo* addresses;struct addrinfo* current_address;char bound_address[1024];char bound_port[64];int opt_on = 1;struct addrinfo hints = {.ai_family   = AF_UNSPEC,.ai_socktype = SOCK_STREAM,.ai_protocol = IPPROTO_TCP};/* Client */struct sockaddr_in client_addr;socklen_t client_addr_len;int connected_socket_fd;/* Arguments */char* listen_address = NULL; /* Default address of INADDR_ANY */char* listen_port = "4822";  /* Default port */char* pidfile = NULL;int opt;int foreground = 0;/* General */int retval;/* Parse arguments */while ((opt = getopt(argc, argv, "l:b:p:f")) != -1) {if (opt == 'l') {listen_port = strdup(optarg);}else if (opt == 'b') {listen_address = strdup(optarg);}else if (opt == 'f') {foreground = 1;}else if (opt == 'p') {pidfile = strdup(optarg);}else {fprintf(stderr, "USAGE: %s"" [-l LISTENPORT]"" [-b LISTENADDRESS]"" [-p PIDFILE]"" [-f]\n", argv[0]);exit(EXIT_FAILURE);}}/* Log start */printf("daemon (%s) start\n", argv[0]);/* Get addresses for binding */if ((retval = getaddrinfo(listen_address, listen_port,&hints, &addresses))) {printf("Error parsing given address or port: %s",gai_strerror(retval));exit(EXIT_FAILURE);}/* Get socket */socket_fd = socket(AF_INET, SOCK_STREAM, 0);if (socket_fd < 0) {printf("Error opening socket: %s", strerror(errno));exit(EXIT_FAILURE);}/* Allow socket reuse */if (setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR,(void*) &opt_on, sizeof(opt_on))) {printf("Unable to set socket options for reuse: %s",strerror(errno));}/* Attempt binding of each address until success */current_address = addresses;while (current_address != NULL) {int retval;/* Resolve hostname */if ((retval = getnameinfo(current_address->ai_addr,current_address->ai_addrlen,bound_address, sizeof(bound_address),bound_port, sizeof(bound_port),NI_NUMERICHOST | NI_NUMERICSERV)))printf("Unable to resolve host: %s",gai_strerror(retval));/* Attempt to bind socket to address */if (bind(socket_fd,current_address->ai_addr,current_address->ai_addrlen) == 0) {printf("Successfully bound socket to ""host %s, port %s", bound_address, bound_port);/* Done if successful bind */break;}/* Otherwise log information regarding bind failure */elseprintf("Unable to bind socket to ""host %s, port %s: %s",bound_address, bound_port, strerror(errno));current_address = current_address->ai_next;}/* If unable to bind to anything, fail */if (current_address == NULL) {printf("Unable to bind socket to any addresses.");exit(EXIT_FAILURE);}/* Daemonize if requested */if (!foreground) {/* Attempt to daemonize process */if (daemonize()) {printf("Could not become a daemon.");exit(EXIT_FAILURE);}}/* Write PID file if requested */if (pidfile != NULL) {/* Attempt to open pidfile and write PID */FILE* pidf = fopen(pidfile, "w");if (pidf) {fprintf(pidf, "%d\n", getpid());fclose(pidf);}/* Fail if could not write PID file*/else {printf("Could not write PID file: %s", strerror(errno));exit(EXIT_FAILURE);}}/* Ignore SIGPIPE */if (signal(SIGPIPE, SIG_IGN) == SIG_ERR) {printf("Could not set handler for SIGPIPE to ignore. ""SIGPIPE may cause termination of the daemon.");}/* Ignore SIGCHLD (force automatic removal of children) */if (signal(SIGCHLD, SIG_IGN) == SIG_ERR) {printf("Could not set handler for SIGCHLD to ignore. ""Child processes may pile up in the process table.");}/* Log listening status */printf("Listening on host %s, port %s", bound_address, bound_port);/* Free addresses */freeaddrinfo(addresses);/* Daemon loop (Use multi_process, not multi_thread)*/for (;;) {pid_t child_pid;/* Listen for connections */if (listen(socket_fd, 5) < 0) {printf("Could not listen on socket: %s", strerror(errno));return 3;}/* Accept connection */client_addr_len = sizeof(client_addr);connected_socket_fd = accept(socket_fd,(struct sockaddr*) &client_addr, &client_addr_len);if (connected_socket_fd < 0) {printf("Could not accept client connection: %s",strerror(errno));return 3;}/** Once connection is accepted, send child into background.** Note that we prefer fork() over threads for connection-handling* processes as they give each connection its own memory area, and* isolate the main daemon and other connections from errors in any* particular client plugin.*/child_pid = fork();/* If error, log */if (child_pid == -1)printf("Error forking child process: %s", strerror(errno));/* If child, start client, and exit when finished */else if (child_pid == 0) {daemon_handle_connection(connected_socket_fd);close(connected_socket_fd);return 0;}/* If parent, close reference to child's descriptor */else if (close(connected_socket_fd) < 0) {printf("Error closing daemon reference to ""child descriptor: %s", strerror(errno));}}/* Close socket */if (close(socket_fd) < 0) {printf("Could not close socket: %s", strerror(errno));return 3;}return 0;}