當(dāng)需要同時(shí)監(jiān)聽多個(gè)文件描述符時(shí)，就需要I/O復(fù)用函數(shù)，I/O復(fù)用函數(shù)有select、poll、epoll，今天主要使用poll函數(shù)。?
poll()接受一個(gè)指向結(jié)構(gòu)'struct pollfd'列表的指針，其中包括了你想測(cè)試的文件描述符和事件。事件由一個(gè)在結(jié)構(gòu)中事件域的比特掩碼確定。當(dāng)前的結(jié)構(gòu)在調(diào)用后將被填寫并在事件發(fā)生后返回。?
函數(shù)原型：?
#include<poll.h>int?poll(struct?pollfd?*fds,?nfds_t?nfds,?int?timeout);struct?pollfd{????int?fd;?????????/*file?descriptor*/????short?events;???/*requested?events*/????short?revents;??/*returned?events*/}函數(shù)參數(shù)：fds是要監(jiān)聽的fd的數(shù)組，nfds是數(shù)組個(gè)數(shù)，timeout?超時(shí)時(shí)間?-1是阻塞；?
函數(shù)說用：通過傳入的events的類型去判斷返回的類型是否一致，如果一致就該干事了。?
events：?
?

?

常量?
說明?
POLLIN?
普通或優(yōu)先級(jí)帶數(shù)據(jù)可讀?
POLLRDNORM?
普通數(shù)據(jù)可讀?
POLLRDBAND?
優(yōu)先級(jí)帶數(shù)據(jù)可讀?
POLLPRI?
高優(yōu)先級(jí)數(shù)據(jù)可讀?
POLLOUT?
普通數(shù)據(jù)可寫?
POLLWRNORM?
普通數(shù)據(jù)可寫?
POLLWRBAND?
優(yōu)先級(jí)帶數(shù)據(jù)可寫?
POLLERR?
發(fā)生錯(cuò)誤?
POLLHUP?
發(fā)生掛起?
POLLNVAL?
描述字不是一個(gè)打開的文件?


接下來是是一個(gè)服務(wù)器監(jiān)聽兩個(gè)socket的例子：?
服務(wù)器代碼：?
#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_POLLFD_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?pollfd?pollfd_arr[MAX_POLLFD_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);??????}??pollfd_arr[0].events?=?POLLRDNORM;/*only?read?event*/pollfd_arr[0].fd?=?server_socket_fd_conn1;pollfd_arr[1].events?=?POLLRDNORM;/*only?read?event*/pollfd_arr[1].fd?=?server_socket_fd_conn2;????while(1){poll_ret?=?poll(?pollfd_arr,?MAX_POLLFD_NUM,-1);if(?pollfd_arr[0].revents?&?POLLRDNORM?){/*connect?1?process?task*/pthread_create(?&thread_conn1,?NULL,?server_conn_handel.Server_Process_Client_Conn1,?(void?*)(&pollfd_arr[0].fd));}if(?pollfd_arr[1].revents?&?POLLRDNORM?){/*connect?2?process?task*/pthread_create(?&thread_conn2,?NULL,?server_conn_handel.Server_Process_Client_Conn2,?(void?*)(&pollfd_arr[1].fd));}sleep(1);}return?0;}客戶端代碼：?
#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);??}解釋：服務(wù)器端監(jiān)聽?ip 127.0.0.1 port 8000和ip 127.0.0.1 port 8001?

IPLC直譯過來是國際私有租賃線路。IPLC產(chǎn)品相對(duì)于普通線路的最大優(yōu)勢(shì)在于不用擔(dān)心IP不可用，節(jié)省下來更換IP的費(fèi)用。另外，IPLC專線的成本比較高，相應(yīng)的延遲時(shí)間比較短，速度也比較快。

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