RAW SOCKETS (PACKET CAPTURING AND FILTERING)

AIM

To implement a program for packet capturing and filtering  between the server and the client systems.

ALGORITHM

Server

1. Set server port address.
2. Using socket function, create a socket for server by specifying server port.
3. Allocate a buffer size.
4. Use TCP socket for sending messages from server to client.
5. Use accept() method to read file by server.
6. Use the input method to read file.
7. Write file to the client.

Client

1. Set client machine address and server port address.
2. Using socket function, create socket for server.
3. Allocate buffer use TCP for receiving message from server to client.
4. Read the file from the server.
5. Read the output from the system.

PROGRAM:

Server

#include<stdio.h>

#include<sys/types.h>

#include<netinet/in.h>

#include<sys/socket.h>

#include<errno.h>

#define SIZE 256

int main()

{

intsrFd,CIFD,len;

structsockaddr_inserver,client;

charbuf[SIZE],buf1[SIZE];

intn,j;

FILE *fp,*fp1;

srFd=socket(AF_INET,SOCK_STREAM,0);

if(srFd<0)

{

printf(“\n Socket error”);

exit(0);

}

bzero(&server,sizeof(server));

server.sin_family=AF_INET;

server.sin_port=htons(2200);

server.sin_addr.s_addr=htons(INADDR_ANY);

if(bind(srFd,(structsockaddr *)&server,sizeof(server))<0)

{

printf(“\n server : bind error”);

close(srFd);

exit(0);

}

if(listen(srFd,1)<0)

{

printf(“\n Listen Error”);

close(CIFD);

exit(0);

}

printf(“\n Server is ready to listen\n”);

len=sizeof(client);

CIFD=accept(srFd,(structsockaddr *)&client,&len);

if(CIFD<0)

{

printf(“\n Accept error”);

close(CIFD);

close(srFd);

exit(0);

}

printf(“Client gets connected\n”);

bzero(&buf,sizeof(buf));

if((n=recv(CIFD,&buf,SIZE,0))<0)

{

printf(“\n Receive Error in Server\n”);

close(srFd);

close(CIFD);

exit(0);

}

buf[n-1]=NULL;

printf(“\n File name %s”,buf);

if((n=send(CIFD,buf,strlen(buf),0))<0)

{

printf(“\n Error”);

close(CIFD);

exit(0);

}

close(srFd);

close(CIFD);

exit(0);

}

Client              

#include<stdio.h>

#include<netinet/in.h>

#include<sys/socket.h>

#include<sys/types.h>

#include<string.h>

#define SIZE 256

int main()

{

int CIFD;

structsockaddr_in client;

charbuf[SIZE];

int n;

if((CIFD=socket(AF_INET,SOCK_STREAM,0))<0)

{

printf(“\n Client Socket Error”);

exit(0);

}

bzero(&client,sizeof(client));

client.sin_family=AF_INET;

client.sin_port=htons(2200);

inet_pton(AF_INET,”127.0.0.1″,&client.sin_addr);

if(connect(CIFD,(structsockaddr *)&client,sizeof(client))<0)

{

printf(“\n connection failed”);

close(CIFD);

exit(0);

}

printf(“\n connection enabled\n”);

printf(“\n Enter source file\n”);

bzero(&buf,sizeof(buf));

if(fgets(buf,SIZE,stdin)==NULL)

{

printf(“\n Failed to get source file name in client\n”);

close(CIFD);

exit(0);

}

if(send(CIFD,buf,strlen(buf),0)<0)

{

printf(“\n Send Error\n”);

close(CIFD);

exit(0);

}

printf(“\n Client message sent\n”);

bzero(&buf,sizeof(buf));

if((n=recv(CIFD,buf,SIZE,0))<0)

{

printf(“\n File name receiver error in client from server\n”);

close(CIFD);

exit(0);

}

printf(“\n Destination file name from server %s”,buf);

buf[n]=NULL;

close(CIFD);

exit(0);

}

OUTPUT

Client

[student@localhost ~]$ ./a.out

Connection Enabled

Enter Source File

Tps.c

Client Message Sent

Destination Filename From Server tps.c

Server

[student@localhost ~]$ ./a.out

Server is ready to listen

Client get connected

Tps.c

RESULT:

Thus raw sockets for packet capturing and filtering has been executed and verified successfully.

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