一个比较实用的连接函数,支持host为域名。
#include <netdb.h> #include <sys/socket.h> #include <sys/types.h> #include <unistd.h> #include <fcntl.h> #include <arpa/inet.h> #include <netinet/tcp.h> #include <iostream> using namespace std; int my_connect(const char *host, int port) { char buf[1024]; struct hostent he, *p; struct sockaddr_in sin; socklen_t len = 0; int sock = -1, ret = 0, err = 0, flags = 0, on = 1; struct timeval t; assert(host != NULL); // invalid server if (host[0] == 0 || port <= 0 || port > 65535) { cout << "find invalid host " << host << " or port " << port << endl; return -1; } //socket if ((sock = socket(PF_INET, SOCK_STREAM, 0)) < 0) { cout << "cannot create socket while connecting to " << host << ":" << port << endl; return -1; } //connect bzero(&sin, sizeof(sin)); sin.sin_addr.s_addr = inet_addr(host); if ((sin.sin_addr.s_addr) == INADDR_NONE) { /* host is not numbers-and-dots ip address */ ret = gethostbyname_r(host, &he, buf, sizeof(buf), &p, &err); if (ret < 0 || err != 0 || p == NULL) { cout << "cannot resolve hostname while connecting to " << host << ":" << port << endl; close(sock); return -1; } memcpy(&sin.sin_addr.s_addr, he.h_addr, sizeof(sin.sin_addr.s_addr)); } sin.sin_family = AF_INET; sin.sin_port = htons(port); flags = fcntl(sock, F_GETFL, 0); fcntl(sock, F_SETFL, flags | O_NONBLOCK); setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on)); ret = connect(sock, (struct sockaddr *) &sin, sizeof(sin)); if (ret == 0) { fcntl(sock, F_SETFL, flags); cout << "connect to " << host << ":" << port << "OK" << endl; return sock; } close(sock); return -1; }