vecloud

当需要同时监听多个文件描述符时，就需要I/O复用函数，I/O复用函数有select、poll、epoll，今天主要使用poll函数。
poll()接受一个指向结构'struct po**d'列表的指针，其中包括了你想测试的文件描述符和事件。事件由一个在结构中事件域的比特掩码确定。当前的结构在调用后将被填写并在事件发生后返回。
函数原型：
#include<poll.h>int poll(struct po**d *fds, nfds_t nfds, int timeout);struct po**d{    int fd;         /*file descriptor*/    short events;   /*requested events*/    short revents;  /*returned events*/}函数参数：fds是要监听的fd的数组，nfds是数组个数，timeout 超时时间 -1是阻塞；
函数说用：通过传入的events的类型去判断返回的类型是否一致，如果一致就该干事了。
events：


常量
说明
POLLIN
普通或优先级带数据可读
POLLRDNORM
普通数据可读
POLLRDBAND
优先级带数据可读
POLLPRI
高优先级数据可读
POLLOUT
普通数据可写
POLLWRNORM
普通数据可写
POLLWRBAND
优先级带数据可写
POLLERR
发生错误
POLLHUP
发生挂起
POLLNVAL
描述字不是一个打开的文件


接下来是是一个服务器监听两个socket的例子：
服务器代码：
#include<stdio.h>#include<stdlib.h>  #include<string.h>  #include<errno.h>  #include<sys/types.h>  #include<sys/socket.h>  #include<netinet/in.h> #include<pthread.h>#include<unistd.h>#include<poll.h>#define MAX_PO**D_NUM 2//#define SERVER_CONN_IP1 "1.1.1.1"//#define SERVER_CONN_IP2 "1.1.1.1"#define DEFAULT_PORT 8000#define BUFF_MAX 1024typedef void(*Server_Rrocess_Thread_Fun)(void *arg);/*thread process function define */typedef struct sever_thread_fun{Server_Rrocess_Thread_Fun Server_Process_Client_Conn1;Server_Rrocess_Thread_Fun Server_Process_Client_Conn2;}Poll_Server_Process_Clinet_FUN_t;/*connect 1 thread function*/void *Poll_Conn1_Process(void *arg){unsigned char ucBufArr[BUFF_MAX] = {0};unsigned long ulSize = 0;int connect_fd ;    printf("come pthread conn1 fun to proess conn1\n");if( (connect_fd = accept( *(int*)arg, (struct sockaddr*)NULL, NULL)) == -1){  printf("accept socket error: %s(errno: %d)",strerror(errno),errno);      }ulSize = recv(connect_fd, ucBufArr, BUFF_MAX, 0);  if(send(connect_fd, "Hello,you are connected 1!\n", 26,0) == -1)  perror("send error");  ucBufArr[ulSize] = '\0';      //sleep(20);printf("recv msg from client: %s\n", ucBufArr);  close(connect_fd);  pthread_exit((void*)1);}/*connect 1 thread function*/void *Poll_Conn2_Process(void *arg){unsigned char ucBufArr[BUFF_MAX] = {0};unsigned long ulSize = 0;int connect_fd ;    printf("come pthread conn2 fun to proess conn2\n");if( (connect_fd = accept( *(int*)arg, (struct sockaddr*)NULL, NULL)) == -1){  printf("accept socket error: %s(errno: %d)",strerror(errno),errno);      }ulSize = recv(connect_fd, ucBufArr, BUFF_MAX, 0);  if(send(connect_fd, "Hello,you are connected 2!\n", 26,0) == -1)  perror("send error");  ucBufArr[ulSize] = '\0';     // sleep(20);printf("recv msg from client: %s\n", ucBufArr);  close(connect_fd);  pthread_exit((void*)2);}int main(){    int poll_ret = 0;pthread_t thread_conn1;pthread_t thread_conn2;    /*socket var*/int server_socket_fd_conn1;int server_socket_fd_conn2;struct sockaddr_in servaddr_conn1;struct sockaddr_in serveraddr_conn2;/*poll var*/    struct po**d po**d_arr[MAX_PO**D_NUM];/*init thread fun*/Poll_Server_Process_Clinet_FUN_t server_conn_handel;server_conn_handel.Server_Process_Client_Conn1 = Poll_Conn1_Process;server_conn_handel.Server_Process_Client_Conn2 = Poll_Conn2_Process;/*create two server socket*/if( (server_socket_fd_conn1 = socket(AF_INET, SOCK_STREAM, 0)) == -1 ){      printf("create socket conn1 error: %s(errno: %d)\n",strerror(errno),errno);      exit(0);      }  if( (server_socket_fd_conn2 = socket(AF_INET, SOCK_STREAM, 0)) == -1 ){      printf("create socket conn2 error: %s(errno: %d)\n",strerror(errno),errno);      exit(0);      }      /*init socket 1 for conn1*/      memset(&servaddr_conn1, 0, sizeof(servaddr_conn1));      servaddr_conn1.sin_family = AF_INET;      servaddr_conn1.sin_addr.s_addr = htonl(INADDR_ANY);     servaddr_conn1.sin_port = htons(DEFAULT_PORT); //if( inet_pton(AF_INET, SERVER_CONN_IP1, &servaddr_conn1.sin_addr.s_addr) <= 0){   //   printf("inet_pton error for %s\n",SERVER_CONN_IP1);    //  exit(0);     // }  /*init socket 2 for conn2*/  memset(&serveraddr_conn2, 0, sizeof(serveraddr_conn2));      serveraddr_conn2.sin_family = AF_INET;      serveraddr_conn2.sin_addr.s_addr = htonl(INADDR_ANY);     serveraddr_conn2.sin_port = htons(DEFAULT_PORT+1); //if( inet_pton(AF_INET, SERVER_CONN_IP2, &serveraddr_conn2.sin_addr.s_addr) <= 0){   //   printf("inet_pton error for %s\n",SERVER_CONN_IP2);    //  exit(0);     // }        /*bind connect 1 socket*/    if( bind(server_socket_fd_conn1, (struct sockaddr*)&servaddr_conn1, sizeof(servaddr_conn1)) == -1){      printf("bind socket error1: %s(errno: %d)\n",strerror(errno),errno);      exit(0);      }  /*bind connect 2 socket*/if( bind(server_socket_fd_conn2, (struct sockaddr*)&serveraddr_conn2, sizeof(serveraddr_conn2)) == -1){      printf("bind socket error2: %s(errno: %d)\n",strerror(errno),errno);      exit(0);      }      /*listen connect 1*/      if( listen(server_socket_fd_conn1, 10) == -1){      printf("listen socket error: %s(errno: %d)\n",strerror(errno),errno);      exit(0);      }  /*listen connect 2*/      if( listen(server_socket_fd_conn2, 10) == -1){      printf("listen socket error: %s(errno: %d)\n",strerror(errno),errno);      exit(0);      }  po**d_arr[0].events = POLLRDNORM;/*only read event*/po**d_arr[0].fd = server_socket_fd_conn1;po**d_arr[1].events = POLLRDNORM;/*only read event*/po**d_arr[1].fd = server_socket_fd_conn2;    while(1){poll_ret = poll( po**d_arr, MAX_PO**D_NUM,-1);if( po**d_arr[0].revents & POLLRDNORM ){/*connect 1 process task*/pthread_create( &thread_conn1, NULL, server_conn_handel.Server_Process_Client_Conn1, (void *)(&po**d_arr[0].fd));}if( po**d_arr[1].revents & POLLRDNORM ){/*connect 2 process task*/pthread_create( &thread_conn2, NULL, server_conn_handel.Server_Process_Client_Conn2, (void *)(&po**d_arr[1].fd));}sleep(1);}return 0;}客户端代码：
#include<stdio.h>  #include<stdlib.h>  #include<string.h>  #include<errno.h>  #include<sys/types.h>  #include<sys/socket.h>  #include<netinet/in.h>    #define BUFF_MAX 1024#define DEFAULT_PORT 8000int main(int argc, char** argv)  {      int    sockfd, n,rec_len;      char    recvline[BUFF_MAX], sendline[BUFF_MAX];      char    buf[BUFF_MAX];      struct sockaddr_in    servaddr;          if( argc != 2){      printf("usage: ./client <ipaddress>\n");      exit(0);      }        /*create socket*/    if( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){      printf("create socket error: %s(errno: %d)\n", strerror(errno),errno);      exit(0);      }      memset(&servaddr, 0, sizeof(servaddr));      servaddr.sin_family = AF_INET;      servaddr.sin_port = htons(DEFAULT_PORT/*+1/);/*DEFAULT_PORT is connect 1 to server,DEFAULT_PORT+1 is connect 2 to server*/  /*string ip to int ip*/    if( inet_pton(AF_INET, argv[1], &servaddr.sin_addr) <= 0){      printf("inet_pton error for %s\n",argv[1]);      exit(0);      }      /*connect server*/    if( connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0){      printf("connect error: %s(errno: %d)\n",strerror(errno),errno);      exit(0);      }      printf("send msg to server: \n");      fgets(sendline, BUFF_MAX, stdin);  /*write data to sockfd*/    if( send(sockfd, sendline, strlen(sendline), 0) < 0)      {      printf("send msg error: %s(errno: %d)\n", strerror(errno), errno);      exit(0);      }  /*read socket data*/    if((rec_len = recv(sockfd, buf, BUFF_MAX,0)) == -1) {         perror("recv error");         exit(1);      }      buf[rec_len]  = '\0';      printf("Received : %s \n",buf);  /*colse socket*/    close(sockfd);      exit(0);  }解释：服务器端监听 ip 127.0.0.1 port 8000和ip 127.0.0.1 port 8001

IPLC直译过来是国际私有租赁线路。IPLC产品相对于普通线路的最大优势在于不用担心IP不可用，节省下来更换IP的费用。另外，IPLC专线的成本比较高，相应的延迟时间比较短，速度也比较快。