UDP socket programming
Client-side program:
#include<stdio.h>
#include<stdlib.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<string.h>
#include<netdb.h>
int main(int argc, char * argv[])
{
int sockfd,bindfd,fromlen,n;
struct sockaddr_in server, from;
struct hostent *hp;
char buff[50];
if(argc<3)
{
printf("insufficient argument");
exit(1);
}
sockfd=socket(AF_INET,SOCK_DGRAM,0);
if(sockfd<0)
{
printf("could not create the socket.");
exit(1);
}
server.sin_family=AF_INET;
server.sin_port=htons(atoi(argv[2]));
hp=gethostbyname(argv[1]);
memcpy((char*)hp->h_addr,(char *)&server.sin_addr.s_addr,hp->h_length);
fromlen=sizeof(server);
printf("Enter the value to request the server:");
fgets(buff,sizeof(buff),stdin);
n=sendto(sockfd,buff,sizeof(buff),0,(struct sockaddr *)&server,fromlen);
if(n<0)
{
printf("could not send message.");
}
n=recvfrom(sockfd,buff,50,0,(struct sockaddr *)&server,&fromlen);
if(n<0)
{
printf("No data to receive.");
}
printf("Response sent by server is:%s",buff);
return 0;
}
Server Side Program:
#include<stdio.h>
#include<stdlib.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<string.h>
#include<netdb.h>
int main(int argc, char * argv[])
{
int sockfd,bindfd,fromlen,n;
struct sockaddr_in server;
struct sockaddr_in from;
char buff[50];
if(argc<2)
{
printf("insufficient argument");
exit(1);
}
sockfd=socket(AF_INET,SOCK_DGRAM,0);
if(sockfd<0)
{
printf("could not create the socket.");
exit(1);
}
memset((char*)&server,0,sizeof(server));
server.sin_family=AF_INET;
server.sin_port=htons(atoi(argv[1]));
server.sin_addr.s_addr=INADDR_ANY;
bindfd=bind(sockfd,(struct sockaddr *)&server,sizeof(server));
if(bindfd<0)
{
printf("could not bind.");
}
fromlen=sizeof(from);
while(1)
{
n=recvfrom(sockfd,buff,sizeof(buff),0,(struct sockaddr *)&from,&fromlen);
if(n<0)
{
printf("No data to receive.");
}
printf("Message received from client is:%s",buff);
printf("type the response to be sent:");
fgets(buff,sizeof(buff),stdin);
n=sendto(sockfd,buff,sizeof(buff),0,(struct sockaddr *)&from,fromlen);
if(n<0)
{
printf("could not send message.");
}
}
return 0;
}
Execution Instruction:
To compile server.c:
$gcc -o exe_filename server.c
To run exe_filename:
$./exe_filename port_number
Whatever may be the executable file name.
port_number should be the 16-bit integer number.
You have to make sure the server is in listen mode.
To compile client.c:
$gcc -o exe_filename1 client.c
To run exe_filename1:
$./exe_filename1 localhost port_number
in place of localhost, you have to mention the IP address of the server, if your server is listening in another machine.
TCP client-server programming in C
