RAW Socket Application 1

In this program two processes p1 and p2 of different system will communicate with each other using row socket. each process will have one raw socket with unique id which will only be known by other so packet sent by one will only be received by other. Here is the program

1. process 1

#include<stdio.h>
#include<stdlib.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<netinet/ip.h>
#include<errno.h>
#include<string.h>
#include<pthread.h>
#include<arpa/inet.h>
#include<netdb.h>
#include<netinet/udp.h>

int sfd;
unsigned short csum (unsigned short *buf, int nwords)
{
 unsigned long sum;
 for (sum = 0; nwords > 0; nwords--)
  sum += *buf++;
 sum = (sum >> 16) + (sum & 0xffff);
 sum += (sum >> 16);
 return ~sum;
}

void *send_msg(void* arg)
{

        printf("send\n");
 char buf[4096],msg[512];
 struct ip* iph=(struct ip*)buf;
iph->ip_hl=5;
iph->ip_v=4;
iph->ip_tos=0;
iph->ip_len=20+sizeof(struct ip);
iph->ip_id=0;
 iph->ip_off=0;
 iph->ip_ttl=64;
 iph->ip_p=21;
 inet_pton(AF_INET,"127.0.0.1",&(iph->ip_src));
 inet_pton(AF_INET,"127.0.0.1",&(iph->ip_dst));
 iph->ip_sum=csum((unsigned short*)buf,iph->ip_len>>1);
int one =1;
 const int *val=&one;
 if(setsockopt(sfd,IPPROTO_IP,IP_HDRINCL,val,sizeof(one))<0)
 {
  printf("hdr include error\n");
 }



struct sockaddr_in server;
 server.sin_family=AF_INET;
 server.sin_port=htons(3500);
 server.sin_addr.s_addr=inet_addr("127.0.0.1");
 while(1)
 {
  fgets(msg,512,stdin);
  strcpy(buf+5*4,msg);
  if(sendto(sfd,buf,iph->ip_len,0,(struct sockaddr*) &server,sizeof server)<0)
   perror("Send error\n");
 }





}
void *recv_msg(void* arg)
{
printf("receive\n");
 char buf[4096];
 struct ip* ipheader=(struct ip*)buf;
 struct sockaddr_in client;
 int length;
 while(1)
 {
  if(recvfrom(sfd,buf,4096,0,(struct sockaddr*) &client,&length)<0)
   perror("receive error\n");


  printf("version is:%d\n",ipheader->ip_v);
  printf("header length:%d\n",ipheader->ip_hl*4);
  printf("service:%d\n",ipheader->ip_tos);
  printf("len:%d\n",ipheader->ip_len);
  printf("sequence id:%d\n",ipheader->ip_id);
  printf("frag offset:%d\n",ipheader->ip_off);
  printf("ttl:%d\n",ipheader->ip_ttl);
  printf("Higher level protocol:%u\n",ipheader->ip_p);
  printf("Check Sum:%d\n",ipheader->ip_sum);
  printf("Source addr:%s\n",inet_ntoa(ipheader->ip_src));
  printf("Destination addr:%s\n\n\n",inet_ntoa(ipheader->ip_dst));

  printf("msg received is:%s\n",buf+sizeof(struct ip));
 }

}

int main()
{


sfd=socket(AF_INET,SOCK_RAW,20);//here 20 is uinque protocol
if(sfd==-1)
{

perror("socket...");exit(1);
}
pthread_t t1,t2;
pthread_create(&t1,NULL,send_msg,NULL);
pthread_create(&t2,NULL,recv_msg,NULL);
pthread_join(t1,NULL);
pthread_join(t2,NULL);

return 0;
}

2. process 2

#include<stdio.h>
#include<stdlib.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<netinet/ip.h>
#include<errno.h>
#include<string.h>
#include<pthread.h>
#include<arpa/inet.h>
#include<netdb.h>
#include<netinet/udp.h>

int sfd;
unsigned short csum (unsigned short *buf, int nwords)
{
 unsigned long sum;
 for (sum = 0; nwords > 0; nwords--)
  sum += *buf++;
 sum = (sum >> 16) + (sum & 0xffff);
 sum += (sum >> 16);
 return ~sum;
}

void *send_msg(void* arg)
{

        printf("send\n");
 char buf[4096],msg[512];
 struct ip* iph=(struct ip*)buf;
iph->ip_hl=5;
iph->ip_v=4;
iph->ip_tos=0;
iph->ip_len=20+sizeof(struct ip);
iph->ip_id=0;
 iph->ip_off=0;
 iph->ip_ttl=64;
 iph->ip_p=20;
 inet_pton(AF_INET,"127.0.0.1",&(iph->ip_src));
 inet_pton(AF_INET,"127.0.0.1",&(iph->ip_dst));
 iph->ip_sum=csum((unsigned short*)buf,iph->ip_len>>1);
int one =1;
 const int *val=&one;
 if(setsockopt(sfd,IPPROTO_IP,IP_HDRINCL,val,sizeof(one))<0)
 {
  printf("hdr include error\n");
 }



struct sockaddr_in server;
 server.sin_family=AF_INET;
 server.sin_port=htons(3500);
 server.sin_addr.s_addr=inet_addr("127.0.0.1");
 while(1)
 {
  fgets(msg,512,stdin);
  strcpy(buf+5*4,msg);
  if(sendto(sfd,buf,iph->ip_len,0,(struct sockaddr*) &server,sizeof server)<0)
   perror("Send error\n");
 }





}
void *recv_msg(void* arg)
{
printf("receive\n");
 char buf[4096];
 struct ip* ipheader=(struct ip*)buf;
 struct sockaddr_in client;
 int length=16;
 while(1)
 {
  if(recvfrom(sfd,buf,2000,0,(struct sockaddr*) &client,&length)<0)
   perror("receive error\n");


  printf("version is:%d\n",ipheader->ip_v);
  printf("header length:%d\n",ipheader->ip_hl*4);
  printf("service:%d\n",ipheader->ip_tos);
  printf("len:%d\n",ipheader->ip_len);
  printf("sequence id:%d\n",ipheader->ip_id);
  printf("frag offset:%d\n",ipheader->ip_off);
  printf("ttl:%d\n",ipheader->ip_ttl);
  printf("Higher level protocol:%u\n",ipheader->ip_p);
  printf("Check Sum:%d\n",ipheader->ip_sum);
  printf("Source addr:%s\n",inet_ntoa(ipheader->ip_src));
  printf("Destination addr:%s\n\n\n",inet_ntoa(ipheader->ip_dst));

  printf("msg received is:%s\n",buf+sizeof(struct ip));
 }

}

int main()
{


sfd=socket(AF_INET,SOCK_RAW,21);//here 21 is unique protocol
if(sfd==-1)
{

perror("socket...");exit(1);
}
pthread_t t1,t2;
pthread_create(&t1,NULL,send_msg,NULL);
pthread_create(&t2,NULL,recv_msg,NULL);
pthread_join(t1,NULL);
pthread_join(t2,NULL);

return 0;
}