在linux下玩转带有超时时间的connect函数

吾爱主题阅读：171 2024-04-05 15:04:56 评论：0

在之前的文章中，我们在Windows下玩过带有超时时间的，本文我们在linux下来玩。在某次面试中，还被遇到了这个问题，有意思。

直接上客户端代码：

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 #include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netdb.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <ctype.h> #include <errno.h> #include <malloc.h> #include <netinet/in.h> #include <arpa/inet.h> #include <sys/ioctl.h> #include <stdarg.h> #include <fcntl.h> #include <time.h> int main( int argc, char *argv[]) // 注意输入参数, 带上ip和port { int sockClient = socket(AF_INET, SOCK_STREAM, 0); struct sockaddr_in addrSrv; addrSrv.sin_addr.s_addr = inet_addr(argv[1]); addrSrv.sin_family = AF_INET; addrSrv.sin_port = htons( atoi (argv[2])); fcntl(sockClient, F_SETFL, fcntl(sockClient, F_GETFL, 0)|O_NONBLOCK); int iRet = connect(sockClient, ( const struct sockaddr *)&addrSrv, sizeof ( struct sockaddr_in)); printf ( "connect iRet is %d, errmsg:%s\n" , iRet, strerror ( errno )); // 返回-1不一定是异常 if (iRet != 0) { if ( errno != EINPROGRESS) { printf ( "connect error:%s\n" , strerror ( errno )); } else { struct timeval tm = {5, 0}; fd_set wset, rset; FD_ZERO(&wset); FD_ZERO(&rset); FD_SET(sockClient, &wset); FD_SET(sockClient, &rset); int time1 = time (NULL); int n = select(sockClient + 1, &rset, &wset, NULL, & tm ); int time2 = time (NULL); printf ( "time gap is %d\n" , time2 - time1); if (n < 0) { printf ( "select error, n is %d\n" , n); } else if (n == 0) { printf ( "connect time out\n" ); } else if (n == 1) { if (FD_ISSET(sockClient, &wset)) { printf ( "connect ok!\n" ); fcntl(sockClient, F_SETFL, fcntl(sockClient, F_GETFL, 0) & ~O_NONBLOCK); } else { printf ( "unknow error:%s\n" , strerror ( errno )); } } else { printf ( "oh, not care now, n is %d\n" , n); } } } printf ( "I am here!\n" ); getchar (); close(sockClient); return 0; }