Today we are going to show you to write simple C level Client – Server Networking & Communication program. This Program and methods are base to create any communication software like whatsapp, fb chat or other, because each connected terminal’s chat goes via server and then routed to device. So this is fist step for communication.
Step 1 : Understand Client Server Communication architecture from book
Step 2 : Run this client and Server code, modify and understand.
Step 3: Enjoy :)
Client Code
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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define RAND_MAX 3
int main(int argc, char *argv[])
{
int sockfd;//client & Main Server
int c_len;
int i,j,rc;
char buff[100];
struct sockaddr_in c_address;
printf("**********This is the client program*************\n");
sockfd=socket(AF_INET, SOCK_STREAM,0);
c_address.sin_family = AF_INET;
c_address.sin_addr.s_addr = inet_addr("127.0.0.1");
c_address.sin_port = htons(7734);
c_len=sizeof(c_address);
rc=connect(sockfd, (struct sockaddr *)&c_address, c_len);
if(rc==1){
perror("Error in Client-Server Connect");
exit(0);
}
while(1){
printf("Enter Data(Buffer)\n");
gets(buff);
send(sockfd,buff,100,0);
}//while endeds
close (sockfd);
return(0);
}//main ended
Server Code
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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define RAND_MAX 3
int main(int argc, char *argv[])
{
int s_sockfd, c_sockfd;//client & Main Server
int sc[4];//child servers pids
int sc_sockfd[4];//Child Server Socket IDs
int s_len, c_len;
int i,j,rc;
long int rand;
char buff[100];
struct sockaddr_in s_add;
struct sockaddr_in c_add;
if(s_sockfd=socket(AF_INET,SOCK_STREAM,0)<0)
perror("Unable to create SOCKET :");
bzero((char *)&s_add,sizeof(s_add));
s_add.sin_family = AF_INET;
s_add.sin_addr.s_addr = htons(INADDR_ANY);
s_add.sin_port = htons(7766);
s_len=sizeof(s_add);
if(bind(s_sockfd, (struct sockaddr *) &s_add, s_len)<0)
{
perror("Error in ''Bind'' \n:");
exit(0);
}
if(listen(s_sockfd,10)<0)
{
perror("Error in ''Listen'' \n:");
exit(0);
}
for(i=0;i<4;i++)
{
sc[i]=fork();//four child server created;
if(sc[i] < 0)
perror("Error in Child server \n");
}//e o for i<4 loop
while(1){
flag:
rand=random();//random numbers in the range from 0 to RAND_MAX
if(rand>3)
goto flag;
if(sc[rand]==0){
c_len = sizeof(c_add);
c_sockfd = accept( sc[rand], (struct sockaddr *) &c_add, c_len);
printf("After accept()");
if(c_sockfd<0)
{
printf("Accept error\n");
exit(0);
}
//close(s_sockfd);//dnt close it becuse child server will resend data to it
dup2(c_sockfd,0);//std ip
dup2(c_sockfd,1);//std op
rc = recv(c_sockfd,buff,100,0);/*buff received from client*/
printf("Received from client data => %s",buff);
send(s_sockfd,buff,100,0);/*now resend it*/
}//if sc[r-1]==0 ended //child ended
}//while ended
rc = recv(sc[rand],buff,100,0); //received from child server
printf("Received at Main Server = >%s",buff);
close (s_sockfd);
return(0);
}//main ended