This document contains code for an ARP server and client program written in C. The server code creates a socket, binds it to port 7564, and listens for connections from clients. When a client connects, the server receives an IP address from the client, looks up the corresponding MAC address, and sends it back to the client. The client code connects to the server socket, prompts the user for an IP address, sends it to the server, receives the MAC address response, and prints it.

1. /* SERVER */
#include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<stdlib.h>
#include<unistd.h>
#include<string.h>
#include<errno.h>
#define port 7564
int main()
{
int sock,con,byte_rec,i=0;
char send_data[1024],rec_data[1024];
struct sockaddr_in ser,cli;
int sin_size;
char ip[5][20]={"127.0.0.1","127.0.0.2","127.0.0.3","127.0.0.4","127.0.0.5"};
char mac[5][20]={"15.8.12.0.0.1","15.8.12.0.0.2","15.8.12.0.0.3","15.8.12.0.0.4","15.8.12.0.0.5"};
//socket creation
if((sock=socket(AF_INET,SOCK_STREAM,0))==-1)

2. {
perror("Socketn");
exit(1);
}
ser.sin_family=AF_INET;
ser.sin_port=htons(port);
ser.sin_addr.s_addr=INADDR_ANY;
bzero(&(ser.sin_zero),8);
//binding the socket
if(bind(sock,(struct sockaddr*)&ser,sizeof(struct sockaddr))==-1)
{
perror("can't bindn");
exit(1);
}
//listening to clients connection request
if(listen(sock,3)==-1)
{
perror("listenn");
exit(1);
}
printf("Waiting n");

3. sin_size=sizeof(struct sockaddr_in);
//accepting connection of client
con=accept(sock,(struct sockaddr*)&cli,&sin_size);
printf("Connectedn");
while(1)
{
//receiving data from client
byte_rec=recv(con,rec_data,1024,0);
rec_data[byte_rec]='0';
if(strcmp(rec_data,"end")==0)
{
//closing socket
close(con);
close(sock);
break;
}
else
printf("Received IP address=%sn",rec_data);
for(i=0;i<5;i++)
{
if(strcmp(ip[i],rec_data)==0)
{
strcpy(send_data,mac[i]);
printf("Mac address %s sent to clientnn",mac[i]);

4. break;
}
}
//sending data to client
send(con,send_data,strlen(send_data),0);
}
return 0;
}
/*CLIENT*/
#include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<stdlib.h>
#include<unistd.h>
#include<string.h>
#include<netdb.h>
#include<errno.h>
#define port 7564

5. int main()
{
int i,sock,byte_rec;
char send_data[1024],rec_data[1024];
char ip[5][20]={"127.0.0.1","127.0.0.2","127.0.0.3","127.0.0.4","127.0.0.5"};
struct hostent *host;
struct sockaddr_in ser,cli;
host=gethostbyname("127.0.0.1");
//socket creation
if((sock=socket(AF_INET,SOCK_STREAM,0))==-1)
{
perror("Socketn");
exit(1);
}
printf("socket createdn");
ser.sin_family=AF_INET;
ser.sin_port=htons(port);
ser.sin_addr= *((struct in_addr *)host->h_addr);
bzero(&(ser.sin_zero),8);
//connecting to server
if(connect(sock,(struct sockaddr*)&ser,sizeof(struct sockaddr))==-1)

6. {
perror("connectn");
exit(1);
}
while(1)
{
//sending data to server
printf("nEnter the IP address : ");
scanf("%s",send_data);
loop1:
for(i=0;i<5;i++)
{
if((strcmp(ip[i],send_data)==0)||(strcmp(send_data,"end")==0))
goto loop2;
}
if(strcmp(ip[i],send_data)!=0)
{
printf("SORRY!! Enter a VALID IP ADDRESS");
printf("nEnter the IP address:n");
scanf("%s",send_data);
goto loop1;
}

7. loop2:
if(strcmp(send_data,"end")!=0)
{
send(sock,send_data,strlen(send_data),0);
}
else
{
send(sock,send_data,strlen(send_data),0);
//closing socket
close(sock);
break;
}
//receiving data from server
byte_rec=recv(sock,rec_data,1024,0);
rec_data[byte_rec]='0';
printf("Received MAC address = %snn",rec_data);
}
return 0;
}
Output
[12mcs009@mepcolinux:~/networkslab]cat arpoutput.txt
[12mcs009@mepcolinux:~]vi arpserver.c

8. [12mcs009@mepcolinux:~]cc arpserver.c
[12mcs009@mepcolinux:~]./a.out
Waiting
Connected
Received IP address=127.0.0.5
Mac address 15.8.12.0.0.5 sent to client
[12mcs009@mepcolinux:~]vi arpclient.c
[12mcs009@mepcolinux:~]cc arpclient.c
[12mcs009@mepcolinux:~]./a.out
socket created
Enter the IP address : 127.0.0.5
Received MAC address = 15.8.12.0.0.5
[12mcs009@mepcolinux:~/networkslab]