Simple Network Proxy Programming Based on Visual C ++ in Windows core programming code analysis (59)

In general, it is a network signal jump, that is, let the network request signal send a request to the website you want to visit through a third party (proxy, then the website will regard it as a third request to him, and then verify whether it meets his requirements. Of course, the signal reception is the same. When you want to receive signals, we will think that we receive a third-party network signal and will not verify it. The content and address of the website you actually visit!

Advantages of using a proxy server to connect to a network

(1) set the user verification and accounting functions, which can be recorded by users. unregistered users do not have the right to access the Internet through the proxy server. The user's access time, access location, and information traffic are analyzed.

(2) perform hierarchical management on users, set access permissions for different users, filter external or internal Internet addresses, and set different access permissions.

(3) Add a buffer to increase the access speed and create a buffer for frequently accessed addresses, greatly improving the access efficiency of popular sites. Usually, the proxy server sets a large hard disk buffer (which may be several GB or larger). When external information passes, it is also saved to the buffer, when other users access the same information again, the information is directly retrieved from the buffer and transmitted to the user to Improve the access speed.

(4) connecting the Intranet to the Internet and acting as a firewall: Because All Intranet users access the outside world through the proxy server, only one IP address is mapped, so the outside world cannot access the Intranet directly; you can also set IP address filtering to restrict Intranet access to the outside.

 

Next we will practice a simple network proxy.

 

 

#include <stdio.h>#include <stdlib.h>#include <errno.h>#include <winsock2.h> #include <io.h>#pragma comment(lib, "ws2_32.lib")#define MAXSIZE                        20480struct TransferSocket {     SOCKET fd1;     SOCKET fd2;};void ClientThread(LPVOID data);int ConnectHost(int SocketSer, char* server, int port);//************************************************************************************VOID main(int argc, char* argv[]){char ServerHost[256] = {0};    int ClientPort=0, ServerPort=0;    WSADATA wsadata;    WSAStartup(MAKEWORD(1, 1), &wsadata);    if (argc != 4){ printf("example: Proxy.exe 8181 68.13.145.77 8181"); return;}    ClientPort = atoi(argv[1]);strcpy(ServerHost, argv[2]);    ServerPort = atoi(argv[3]);                         SOCKET SocketListen,SocketClient,SocketServer;    struct sockaddr_in remote;    int size;    char buffer[1024];    HANDLE hThread=NULL;    TransferSocket sock;    DWORD dwThreadID;    if (ClientPort > 65535 || ClientPort < 1)    {           printf("Client connectPort invalid.\r\n");           return;    }     if (ServerPort > 65535 || ServerPort < 1)     {           printf("Server connectPort invalid.\r\n");           return;     }          memset(buffer,0,1024); //----------     SocketListen=socket(AF_INET,SOCK_STREAM,0);     if(SocketListen<=0)     {           printf("Create socket error.\r\n");           return;     }      //-----------     struct sockaddr_in srvaddr;     int on=1;         memset(&srvaddr, 0, sizeof(struct sockaddr));     srvaddr.sin_port=htons(ClientPort);     srvaddr.sin_family=AF_INET;     srvaddr.sin_addr.s_addr=htonl(INADDR_ANY);       setsockopt(SocketListen,SOL_SOCKET,SO_REUSEADDR, (char*)&on,sizeof(on));      if(bind(SocketListen,(struct sockaddr *)&srvaddr,sizeof(struct sockaddr))<0)     {           printf("Listen socket bind error.\r\n");           return;     }     if(listen(SocketListen,8)<0)     {           printf("Socket Listen error.\r\n");           return;     }          size=sizeof(struct sockaddr);     while(1)     {           printf("Waiting for Client ......\r\n");                 if((SocketClient=accept(SocketListen,(struct sockaddr *)&remote,&size))<0)           {                 printf("Accept error.\r\n");                 continue;           }           printf("Accept a Client from %s:%d ......\r\n",           inet_ntoa(remote.sin_addr), ntohs(remote.sin_port));   SocketServer=socket(AF_INET,SOCK_STREAM,0);           if(SocketServer <= 0)   {   printf("Create socket error.\r\n");       closesocket(SocketClient);               return;   }                                 printf("Make a Connection to %s:%d ......\r\n",ServerHost,ServerPort);           if(ConnectHost(SocketServer,ServerHost,ServerPort)==0)           {                 closesocket(SocketServer);                 closesocket(SocketClient);                 continue;           }                      printf("Connect successed!\r\n");           sock.fd1 = SocketClient;           sock.fd2 = SocketServer;           hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)ClientThread, (LPVOID)&sock, 0, &dwThreadID);            if(hThread == NULL)            {                 TerminateThread(hThread, 0);                 return;           }           Sleep(1000);           printf("CreateThread successed!\r\n\n");     }     WSACleanup();     return;}void ClientThread(LPVOID data){     SOCKET fd1, fd2;     TransferSocket *sock;     struct timeval timeset;     fd_set readfd,writefd;     int result,i=0;     char read_in1[MAXSIZE],send_out1[MAXSIZE];     char read_in2[MAXSIZE],send_out2[MAXSIZE];     int read1=0,totalread1=0,send1=0;     int read2=0,totalread2=0,send2=0;     int sendcount1,sendcount2;     int maxfd;     int structsize1,structsize2;     char tmpbuf[100];     sock = (TransferSocket *)data;     fd1 = sock->fd1;     fd2 = sock->fd2;     memset(tmpbuf,0,100);     structsize1=sizeof(struct sockaddr);     structsize2=sizeof(struct sockaddr);      maxfd=max(fd1,fd2)+1;     memset(read_in1,0,MAXSIZE);     memset(read_in2,0,MAXSIZE);     memset(send_out1,0,MAXSIZE);     memset(send_out2,0,MAXSIZE);       timeset.tv_sec=1000;     timeset.tv_usec=0;     while(1)     {           FD_ZERO(&readfd);           FD_ZERO(&writefd);                   FD_SET((UINT)fd1, &readfd);           FD_SET((UINT)fd1, &writefd);           FD_SET((UINT)fd2, &writefd);           FD_SET((UINT)fd2, &readfd);                  result=select(maxfd,&readfd,&writefd,NULL,×et);           if((result<0) && (errno!=EINTR))           {                 printf("Select error.\r\n");                 break;           }           else if(result==0)           {                 printf("Socket time out.\r\n");                 break;           }           if(FD_ISSET(fd1, &readfd))   {                 if(totalread1<MAXSIZE)               {                       read1=recv(fd1, read_in1, MAXSIZE-totalread1, 0);                        if((read1==SOCKET_ERROR) || (read1==0))                       {                             printf("Read client data error\r\n");                             break;                       }                       memcpy(send_out1+totalread1,read_in1,read1);                       totalread1+=read1;                       memset(read_in1,0,MAXSIZE);                 }           }           if(FD_ISSET(fd2, &writefd))           {                 int err=0;                 sendcount1=0;                 while(totalread1>0)                 {                       send1=send(fd2, send_out1+sendcount1, totalread1, 0);                       if(send1==0)break;                       if((send1<0) && (errno!=EINTR))                       {                             printf("Send to server error.\r\n");                             err=1;                             break;                       }                                              if((send1<0) && (errno==ENOSPC)) break;                          sendcount1+=send1;                       totalread1-=send1;                  }                                if(err==1) break;                 if((totalread1>0) && (sendcount1>0))                 {                       memcpy(send_out1,send_out1+sendcount1,totalread1);                       memset(send_out1+totalread1,0,MAXSIZE-totalread1);                 }                 else                 memset(send_out1,0,MAXSIZE);           }                       if(FD_ISSET(fd2, &readfd))           {                 if(totalread2<MAXSIZE)                 {                       read2=recv(fd2,read_in2,MAXSIZE-totalread2, 0);                        if(read2==0)break;                       if((read2<0) && (errno!=EINTR))                       {                             printf("Read server data error\r\n\r\n");                             break;                       }                       memcpy(send_out2+totalread2,read_in2,read2);                    totalread2+=read2;                 memset(read_in2,0,MAXSIZE);                 }   }           if(FD_ISSET(fd1, &writefd))   {               int err2=0;               sendcount2=0;               while(totalread2>0)               {                     send2=send(fd1, send_out2+sendcount2, totalread2, 0);                     if(send2==0)break;                     if((send2<0) && (errno!=EINTR))                     {                           printf("Send to client  error.\r\n");                             err2=1;                           break;                     }                     if((send2<0) && (errno==ENOSPC)) break;                     sendcount2+=send2;                     totalread2-=send2;                                     }                 if(err2==1) break;               if((totalread2>0) && (sendcount2 > 0))                {                       memcpy(send_out2, send_out2+sendcount2, totalread2);                       memset(send_out2+totalread2, 0, MAXSIZE-totalread2);                }                else                       memset(send_out2,0,MAXSIZE);           }            Sleep(5);     }        closesocket(fd1);     closesocket(fd2);     printf("\r\n Closed The Two Socket.\r\n"); }int ConnectHost(int SocketSer,char* server,int port){  struct sockaddr_in cliaddr;  struct hostent *ServerHost;  if(!(ServerHost=gethostbyname(server)))  {        printf("Gethostbyname(%s) error:%s\n",server,strerror(errno));        return(0);  }          memset(&cliaddr, 0, sizeof(struct sockaddr));  cliaddr.sin_family=AF_INET;  cliaddr.sin_port=htons(port);  cliaddr.sin_addr=*((struct in_addr *)ServerHost->h_addr);    if(connect(SocketSer,(struct sockaddr *)&cliaddr,sizeof(struct sockaddr))<0)  {        printf("Connect error.\r\n");        return(0);  }  return 1;}