我常用的 socket connect 代码，主要是为了记录非阻塞问题

SOCKET connectToS(){int e=0;struct timeval timeout ; fd_set r;SOCKET s=socket(AF_INET,SOCK_STREAM,0);//设置非阻塞方式连接 unsigned long ul1 = 1; e = ioctlsocket(s,FIONBIO,(unsigned long*)&ul1); if(e==SOCKET_ERROR){ fprintf(stderr,"设置[非阻塞]方式错误，请重新启动！/n");::closesocket (s); return -1; }struct sockaddr_in addr;memset(&addr,0,sizeof(struct sockaddr_in));addr.sin_family = AF_INET;addr.sin_port = htons(SERVERPORT);addr.sin_addr.s_addr = inet_addr(SERVERIP);connect(s,(SOCKADDR*)&addr,sizeof(SOCKADDR));//select 模型，即设置超时 FD_ZERO(&r); FD_SET(s,&r); timeout.tv_sec = 5; //连接超时10秒 timeout.tv_usec =0; e=select(NULL,NULL,&r,NULL,&timeout); if(e<=0) {fprintf(stderr,"连接超时,请检查网络是否可用！/n");::closesocket(s); return -1; }unsigned long ul2= 0; e = ioctlsocket(s,FIONBIO,(unsigned long*)&ul2); if(e==SOCKET_ERROR){fprintf(stderr,"设置[阻塞]方式错误，请重新启动！/n");::closesocket (s); return -1; }return s;}