Linux下socket实现网页抓取 Unicorn 博客频道 CSDN.NET

主要用来和WinSock进行下比较：

--WinSock--

需要初始化：

if( (Ret = WSAStartup(MAKEWORD(1,1), &wsaData) ) != 0 )

{

printf("WSAStartup failed with error %d/n", Ret);

return FALSE;

}

头文件：

--WinSock--

#include <winsock2.h> //header

#pragma comment (lib, "ws2_32.lib") //lib

--Linux--

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <netdb.h>

各个头文件的作用还需要进一步研究

gethostbyname(host)：//从主机名返回地址

这个都是一样的，返回一个struct hostent *的指针。

地址结构：

--WinSock--

SOCKADDR_IN

--Linux--

sockaddr_in

实际上是一样的都是

struct sockaddr_in{

shortsin_family;

unsigned short sin_port;

struct in_addr sin_addr;

charsin_zero[8];

};

(

这个结构是sockaddr的等价结构

struct sockaddr

{

unsigned short sa_family; // address family, AF_XXX

char sa_data[14]; //14 bytes of protocol address

};

)

其中IP地址结构struct in_addr定义如下：

struct in_addr {

union {

struct{

unsigned char s_b1,

s_b2,

s_b3,

s_b4;

} S_un_b;

struct {

unsigned short s_w1,

s_w2;

} S_un_w;

unsigned long S_addr;

} S_un;

};

Socket:

--WinSock--

返回句柄SOCKET，就是socket描述符

--Linux--

比较直接返回int型socket描述符

函数接口都一样

函数例子：

socket (AF_INET, SOCK_STREAM, 0); //TCP

connect(sock, (const sockaddr * )&tcpaddr, sizeof(tcpaddr)); //返回值有不同

--WinSock--

If no error occurs, connect returns zero. Otherwise, it returns SOCKET_ERROR, and a specific error code can be retrieved by calling

WSAGetLastError.

--Linux--

错误返回-1

send(sock_description, message, strlen(message), 0); //返回值不同

--WinSock--

If no error occurs, send returns the total number of bytes sent, which can be less than the number indicated by len. Otherwise, a value of

SOCKET_ERROR is returned, and a specific error code can be retrieved by calling WSAGetLastError.

--Linux--

错误返回-1

recv(sock_description, buffer, sizeof(buffer), 0);//返回值不同

--WinSock--

If no error occurs, recv returns the number of bytes received. If the connection has been gracefully closed, the return value is zero. Otherwise, a

value of SOCKET_ERROR is returned, and a specific error code can be retrieved by calling WSAGetLastError.

--Linux--

错误返回-1

结束：

--WinSock--

closesocket(sock);

if( WSACleanup() == SOCKET_ERROR )

{

printf("WSACleanup failed with error %d /n", WSAGetLastError() );

}

--Linux--

close(sock);

下面是一个Linux下socket一个HTTP协议GET方法的应用：

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <netdb.h>

char*host = "www.hao123.com";

intport = 80;

int main(void)

{

char buffer[512];

int isock;

struct sockaddr_in pin;

struct hostent * remoteHost;

char message[512];

int done = 0;

int chars = 0;

int l = 0;

if( (remoteHost = gethostbyname(host)) == 0 )

{

printf("Error resolving host/n");

exit(1);

}

bzero(message,sizeof(message));

bzero(&pin,sizeof(pin));

pin.sin_family = AF_INET;

pin.sin_port = htons(port);

pin.sin_addr.s_addr = ( (struct in_addr *)(remoteHost->h_addr) )->s_addr;

if( (isock = socket(AF_INET, SOCK_STREAM, 0)) == -1)

{

printf("Error opening socket!/n");

exit(1);

}

sprintf(message, "GET / HTTP/1.1/r/n");

strcat(message, "Host:www.hao123.com/r/n");

strcat(message, "Accept: */*/r/n");

strcat(message, "User-Agent: Mozilla/4.0(compatible)/r/n");

strcat(message, "connection:Keep-Alive/r/n");

strcat(message, "/r/n/r/n");

printf("%s",message);

if( connect(isock, (void *)&pin, sizeof(pin)) == -1 )

{

printf("Error connecting to socket/n");

exit(1);

}

if( send(isock, message, strlen(message), 0) == -1)

{

printf("Error in send/n");

exit(1);

}

while(done == 0)

{

l = recv(isock, buffer, 1, 0);

if( l < 0 )

done = 1;

switch(*buffer)

{

case '/r':

break;

case '/n':

if(chars == 0)

done = 1;

chars = 0;

break;

default:

chars++;

break;

}

printf("%c",*buffer);

}

do

{

l = recv(isock, buffer, sizeof(buffer) - 1, 0);

if( l < 0 )

break;

*(buffer + l) = 0;

fputs(buffer, stdout);

}while( l > 0 );

close(isock);

return 0;

}