socket编程，为何第二个recv出错？

#include <stdio.h>
#include <string>
#include <winsock.h>
#include <winsock2.h>
#include <iostream>
#define MAXLINE 10000
#define SA struct sockaddr
#define SOCKET int

using namespace std;
int main (int argc,char * argv[])
{

 string s1,s2,s3,s4;
 cin>>s1>>s2>>s3>>s4;
 SOCKET sockfd;
 char recvline[MAXLINE+1];
 WSADATA wsaData;
 if (WSAStartup(MAKEWORD(2,1),&wsaData)!=0)
 {
 perror("initial error!");
 WSACleanup();
 exit(1);
 }

 struct sockaddr_in server_addr;
 struct hostent *hp;
 hp=(struct hostent *)malloc(sizeof(struct hostent));
 hp=gethostbyname("www.baidu.com");
 server_addr.sin_family=AF_INET;
 server_addr.sin_port=htons(80);
 memcpy((char*)&server_addr.sin_addr,(char*)hp->h_addr,hp->h_length);


 if ((sockfd=socket(AF_INET,SOCK_STREAM,0))<0)/*判断socket是否出错*/
 {
 perror("socket error");
 exit(1);
 }



 if(connect(sockfd,(SA*)&server_addr,sizeof(server_addr))<0) //连接socket
 {
 perror("connection error!");
 exit(1);
 }

 string strkey=(string)"GET /s?wd="+s2+(string)"&cl=3 HTTP/1.1 "
 "Accept: */* "
 "Referer: http://www.baidu.com/ "
 "Accept-Language: zh-cn "
 "Accept-Encoding: gzip, deflate "
 "User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727) "
 "Host: www.baidu.com "
 "Connection: Keep-Alive ";
 const char* ptrkey =strkey.c_str();
 char bufferkey[2048];
 for (int i=0;bufferkey[i++]=*ptrkey++;);

 if(send(sockfd,bufferkey,sizeof(bufferkey),0)<0) //发送关键字
 {
 perror("send error!");
 exit(1);
 }

 if(recv(sockfd,recvline,MAXLINE,0)<0) //搜索结果返回
 {
 perror("recv error!");
 exit(1);
 }

 string strclick= (string)"GET /w.gif?query="+s2+(string)"&e=959f"/*&e=?不知道怎么处理*/+(string)"&title="+s4+(string)"&url=http%3A//www.rfidinfo.com.cn/Portal/Simple/"
 "Contact_4209.html&spos=4&path=http://www.baidu.com/s?ie=gb2312&bs=rfid&sr=&z=&cl=3&f=8&wd=rfid+"
 "%D0%C5%B4%EF%BB%E3%B4%CF&ct=0&t=1177206870437" /*url怎么处理？*/+
 (string)"HTTP/1.1\nAccept: */*\nReferer: http://www.baidu.com/s?wd="+s2+(string)"&cl=3\nAccept-Language: zh-cn\n"
 "Accept-Encoding: gzip, deflate\n"
 "User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)\n"
 "Host: s.baidu.com\n"
 "Connection: Keep-Alive\n" ;
 const char* ptrclick =strkey.c_str();
 char bufferclick[2048];
 for (int i=0;bufferclick[i++]=*ptrclick++;);

 if(send(sockfd,bufferclick,sizeof(bufferclick),0)<0) //点击搜索结果
 {
 perror("send error!");
 exit(1);
 }

 if(recv(sockfd,recvline,MAXLINE,0)<0) //返回点击内容
 {
 perror("recv error!");
 exit(1);
 }

 closesocket(sockfd);
 free(hp);
 WSACleanup();
 exit(0);
}

12 个解决方案

#1

mark

#2

send时也无法发送get语句是什么原因？

#3

不明白为什么要放到C++版面，全是C风格

#4

这个是用dev c++ 编的要放c版么？

#5

第一次发送/接收数据后，需要关闭socket
第二次应该重新建立socket，然后发送/接收，
如此反复，连绵不绝。。。。。。。

#6

那就是说发送一次新建一次socket？不对吧？

#7

在HTTP协议里是这样的！
服务器已经close了！不信你可以试试看！
在第二次send之前sleep(15)
在sleep是，打开另一个终端窗口用netstat看连接情况连接应该是处在 CLOSE_WAIT状态，这个状态的意思就是对方已经关闭，系统正在等待应用程序调用close以结束这个连接，这也就是CLOSE_WAIT这个状态的由来！

#8

那你的意思是要从
     WSADATA wsaData;
     if (WSAStartup(MAKEWORD(2,1),&wsaData)!=0)
     {
        perror("initial error!");
        WSACleanup();
        exit(1);
     }
开始做么？

#9

从 socket() 到 closesocket()

#10

还是不行根本向百度发不出get请求

#11

发送的请求最后需要"\r\n\r\n"
以下是我改过的程序可以收到回应

#include <cerrno>
#include <string>
#include <iostream>
#include <fstream>
#include <winsock.h>

using namespace std;

#define CRLF2 "\r\n\r\n"
#define CRLF "\r\n"
#define CR "\r"
#define LF "\n"

#define MAX_RECV_LEN 40960
#define SA struct sockaddr
#define SOCKET int

int main (int argc,char * argv[])
{
SOCKET sockfd;
WSADATA wsaData;
struct sockaddr_in server_addr;
struct hostent *hp;

string strSend;
string strRecv;
char bufRecv[MAX_RECV_LEN + 1];

ofstream fout;
size_t posHtml;

int nSend, nRecv;

if (WSAStartup(MAKEWORD(2,1),&wsaData)!=0)
{
perror("initial error!");
WSACleanup();
exit(1);
}

hp=gethostbyname("www.baidu.com");
server_addr.sin_family=AF_INET;
server_addr.sin_port=htons(80);
memcpy((char*)&server_addr.sin_addr,(char*)hp->h_addr,hp->h_length);

if ( (sockfd = socket(AF_INET,SOCK_STREAM,0)) < 0 )
{
perror("socket()");
exit(1);
}

 if( connect(sockfd,(SA*)&server_addr, sizeof(server_addr)) <0 )
 {
 perror("connect()");
 exit(1);
 }

string s;

strSend = "GET /s?wd=" "rfid" "&cl=3 HTTP/1.1" CRLF CRLF;

if( (nSend = send(sockfd, strSend.c_str(), strSend.length() ,0)) <0 )
{
perror("send()");
exit(1);
}

Sleep(5000);
bufRecv[0] = '\0';
if ( (nRecv = recv(sockfd + 1, bufRecv, MAX_RECV_LEN, 0)) < 0 )
{
perror("recv()");
exit(1);
}

bufRecv[nRecv] = '\0';
strRecv = bufRecv;

if ( (strRecv.length() > 0)
&& ( (posHtml = strRecv.find(CRLF2)) != string::npos)
)
{
posHtml += 4;
fout.open("html.log", ios::out | ios::binary | ios::trunc);
fout << strRecv;
fout.close();
system("start html.log");

fout.open("html.html", ios::out | ios::binary | ios::trunc);
fout << strRecv.substr(posHtml);
fout.close();
system("start html.html");
}

closesocket(sockfd);
WSACleanup();

return 0;
}

#12

if ( (nRecv = recv(sockfd + 1, bufRecv, MAX_RECV_LEN, 0)) < 0 )
应该改为
if ( (nRecv = recv(sockfd, bufRecv, MAX_RECV_LEN, 0)) < 0 )

#1