/*********************************************************************************
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* Copyright: (C) 2025 LingYun IoT System Studio
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* All rights reserved.
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*
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* Filename: socketd_poll.c
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* Description: This file is TCP socket server(poll) example program.
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*
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* Version: 1.0.0(10/20/2025)
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* Author: Guo Wenxue <guowenxue@gmail.com>
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* ChangeLog: 1, Release initial version on "10/20/2025 09:48:51 PM"
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*
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********************************************************************************/
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#include <stdio.h>
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#include <string.h>
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#include <errno.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <signal.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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#include <getopt.h>
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#include <ctype.h>
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#include <sys/time.h>
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#include <sys/resource.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <pthread.h>
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#include <poll.h>
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#define BACKLOG 13
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#define MAX_FDS 4096
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#define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))
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int g_stop = 0; /* program stop or not */
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void sig_handler(int signum);
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int socket_init(int port);
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void print_usage(char *progname)
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{
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printf("%s usage: \n", progname);
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printf(" -p(--port): sepcify listen port.\n");
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printf(" -h(--Help): print this help information.\n");
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return ;
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}
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int main(int argc, char **argv)
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{
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int i, j;
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int rv = -1;
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int listen_fd, client_fd = -1;
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int port = 10086;
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int debug = 0;
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struct sockaddr_in cli_addr;
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socklen_t addr_len = sizeof(cli_addr);
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char buf[1024];
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struct pollfd fds_array[MAX_FDS];
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int need_update;
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int nfds = 0;
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int found;
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int ch;
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struct option opts[] = {
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{"debug", no_argument, NULL, 'd'},
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{"port", required_argument, NULL, 'p'},
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{"help", no_argument, NULL, 'h'},
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{NULL, 0, NULL, 0}
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};
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/* 解析命令行参数 */
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while( (ch=getopt_long(argc, argv, "dp:h", opts, NULL)) != -1 )
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{
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switch(ch)
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{
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case 'd':
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debug = 1;
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break;
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case 'p':
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port=atoi(optarg);
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break;
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case 'h':
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print_usage(argv[0]);
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return 0;
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}
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}
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/* 如果不是debug调试运行，就放到后台去运行 */
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if( !debug )
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daemon(0, 0);
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/* 安装信号 */
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signal(SIGTERM, sig_handler); /* capture kill/killall signal */
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signal(SIGINT, sig_handler); /* capture Ctrl+C signal */
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signal(SIGSEGV, sig_handler); /* capture segmentation fault signal */
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signal(SIGPIPE, sig_handler); /* capture socket error signal */
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/* 创建监听套接字 */
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if( (listen_fd = socket_init(port)) < 0 )
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return 2;
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/* 初始化 pollfd 数组 */
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for (i=0; i<ARRAY_SIZE(fds_array); i++)
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{
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fds_array[i].fd = -1;
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fds_array[i].events = 0;
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fds_array[i].revents = 0;
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}
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/* 将 listen_fd 放到 pollfd 数组的第一个元素中 */
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fds_array[0].fd = listen_fd;
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fds_array[0].events = POLLIN;
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nfds = 1;
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need_update = 0; /* 第一次进入循环只有listen_fd, 不需要更新 nfds */
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while( !g_stop )
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{
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/* 接收或关闭客户端时需要重新计算 nfds */
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if( need_update )
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{
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for(i=0, nfds=0; i<ARRAY_SIZE(fds_array); i++)
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{
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if (fds_array[i].fd>0 && i>= nfds )
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nfds = i+1;
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}
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need_update = 0; /* 清除更新标志 */
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}
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/* poll 一直阻塞等待, 永不超时 */
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rv=poll(fds_array, nfds, -1);
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if( rv <= 0 )
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{
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/* poll()超时或有异常发生(如有信号到来)，继续下次循环 */
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printf("poll failure: %s\n", strerror(errno));
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continue;
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}
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/* 程序走到这里说明 rv>0, 有文件描述符发生事件了 */
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/* 检查是不是 listen_fd 发生了事件，如果有说明有新的客户端连接请求到来 */
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if (fds_array[0].revents & POLLIN)
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{
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/* 接收新的客户端连接请求 */
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client_fd = accept(listen_fd, (struct sockaddr*)&cli_addr, &addr_len);
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if(client_fd < 0)
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{
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printf("accept new socket failure: %s\n", strerror(errno));
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continue;
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}
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printf("Accept new client[%s:%d] with fd [%d]\n",
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inet_ntoa(cli_addr.sin_addr), ntohs(cli_addr.sin_port), client_fd);
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/* 从符数组中找一个空位置，将新的客户端文件描述符加进去 */
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found = 0;
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for(i=0; i<ARRAY_SIZE(fds_array) ; i++)
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{
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if( fds_array[i].fd < 0 )
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{
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fds_array[i].fd = client_fd;
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fds_array[i].events = POLLIN;
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found = 1;
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need_update = 1;
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break;
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}
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}
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/* 如果没找到说明客户端太多了，拒绝这个新的客户端连接请求 */
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if( !found )
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{
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printf("accept new client[%d] but full, so refuse it\n", client_fd);
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close(client_fd);
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}
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}
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/* fds_array[0] 是 listen_fd, 其它的则是已经连上的客户端，看是不是它们有数据到来了 */
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for(i=1; i<ARRAY_SIZE(fds_array); i++)
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{
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/* 如果位置是空的就找下一个 */
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if( fds_array[i].fd<0 )
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continue;
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/* 如果有可读事件 */
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if (fds_array[i].revents & POLLIN)
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{
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memset(buf, 0, sizeof(buf));
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if( (rv=read(fds_array[i].fd, buf, sizeof(buf))) <= 0)
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{
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printf("socket[%d] get disconncet\n", fds_array[i].fd);
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close(fds_array[i].fd);
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fds_array[i].fd = -1;
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need_update = 1;
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continue;
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}
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printf("socket[%d] client read %d bytes data: %s\n", fds_array[i].fd, rv, buf);
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/* 将收到的字符串统一转成大写 */
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for(j=0; j<rv; j++)
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{
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buf[i]=toupper(buf[i]);
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}
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/* 将处理后的数据返回给客户端 */
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rv=write(fds_array[i].fd, buf, rv);
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if(rv <= 0)
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{
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printf("socket[%d] write failure: %s\n", fds_array[i].fd, strerror(errno));
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/* 客户端关闭时要把这个位置空出来 */
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close(fds_array[i].fd);
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fds_array[i].fd = -1;
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need_update = 1;
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continue;
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}
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}
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/* 处理异常或挂起事件 */
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if (fds_array[i].revents & (POLLERR | POLLHUP | POLLNVAL))
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{
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printf("socket[%d] closed or error\n", fds_array[i].fd);
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close(fds_array[i].fd);
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fds_array[i].fd = -1;
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need_update = 1;
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continue;
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}
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}
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}
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close(listen_fd);
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return 0;
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}
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void sig_handler(int signum)
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{
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switch(signum)
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{
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case SIGTERM:
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printf("SIGTERM signal detected(kill/killall)\n");
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break;
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case SIGSEGV:
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printf("SIGSEGV signal detected(segmentation fault)\n");
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break;
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case SIGPIPE:
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printf("SIGPIPE signal detected(socket error)\n");
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break;
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case SIGINT:
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printf("SIGINT signal detected(Ctrl+C)\n");
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break;
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default:
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break;
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}
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g_stop = 1;
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}
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int socket_init(int port)
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{
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int listen_fd;
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int reuse = 1;
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struct rlimit limit;
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struct sockaddr_in serv_addr;
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/* set Max. fd limit */
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getrlimit(RLIMIT_NOFILE, &limit);
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limit.rlim_cur = limit.rlim_max;
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setrlimit(RLIMIT_NOFILE, &limit);
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/* create TCP socket */
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listen_fd = socket(AF_INET, SOCK_STREAM, 0);
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if(listen_fd < 0 )
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{
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printf("create socket failure: %s\n", strerror(errno));
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return -1;
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}
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/* resolve the "Address already in use" error when using bind() */
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setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse));
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/* bind socket server information */
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memset(&serv_addr, 0, sizeof(serv_addr));
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serv_addr.sin_family = AF_INET;
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serv_addr.sin_port = htons(port);
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serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
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if( bind(listen_fd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0 )
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{
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printf("bind socket failure: %s\n", strerror(errno));
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return -2;
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}
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printf("socket[%d] bind on port[%d] for all IP address ok\n", listen_fd, port);
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/* start listen socket */
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listen(listen_fd, BACKLOG);
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return listen_fd;
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}
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