怎么连接失败，求解释
#include <winsock2.h>#pragma comment(lib,"ws2_32.lib")#include <cstdlib>#include <string>#include <iostream>using namespace std;int _tmain(int argc, _TCHAR* argv[]){ /*定义socket数据变量*/ WSADATA wsd; SOCKET sHost; // 与服务器通信的socket SOCKADDR_IN serAddr; //服务器地址 char buf[BUF_SIZE]; int retVal; if(WSAStartup(MAKEWORD(2,2),&wsd) != 0) { printf("初始化失败!\n"); return -1; } //创建Socket sHost=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP); if(sHost == INVALID_SOCKET) { printf("Socket failed!\n"); WSACleanup(); return -1; } //设置服务器地址; serAddr.sin_family=AF_INET; serAddr.sin_addr.S_un.S_addr=inet_addr("192.168.5.205"); serAddr.sin_port=htons(9990);//设置通信端口; //连接到服务器 retVal=connect(sHost,(const sockaddr*)&serAddr,sizeof(serAddr)); if(retVal == SOCKET_ERROR) { printf("Connect failed\n"); closesocket(sHost); return -1; } //发送消息 while(true) { printf("Please input a string to send: "); string str; getline(cin,str); ZeroMemory(buf,BUF_SIZE);//清空缓冲队列; strcpy(buf,str.c_str()); retVal=send(sHost,buf,strlen(buf),0); if(retVal == SOCKET_ERROR) { printf("send faild\n"); closesocket(sHost); WSACleanup(); break; } retVal=recv(sHost,buf,strlen(buf),0); printf("Recv from Server: %s\n",buf); if(strcmp(buf,"quit") == 0) { printf("quit!\n"); break; } } closesocket(sHost); WSACleanup(); return 0;}//刚学习网络编程，前辈们帮我指点一下，为什么会连接失败呢