/* udpserver.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <ctype.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <errno.h>
#define MAXLINE 80
int port = 8000;
int
main( void )
{
struct sockaddr_in sin;
struct sockaddr_in rin;
int sock_fd;
int address_size;
char buf[MAXLINE];
char str[INET_ADDRSTRLEN];
int i;
int n;
int len;
bzero( &sin, sizeof( sin ) );
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = INADDR_ANY;
sin.sin_port = htons( port );
sock_fd = socket( AF_INET, SOCK_DGRAM, 0 );
if ( sock_fd == -1 )
{
perror( "call to socket" );
exit( 1 );
}
n = bind( sock_fd, ( struct sockaddr * ) &sin, sizeof( sin ) );
if ( n == -1 )
{
perror( "call to bind" );
exit( 1 );
}
while ( 1 )
{
address_size = sizeof( rin );
n = recvfrom( sock_fd, buf, MAXLINE, 0, ( struct sockaddr * ) &rin,
&address_size );
if ( n == -1 )
{
perror( "call to recvfrom.\n" );
exit( 1 );
}
printf( "received from client %s at port %d: %s\n",
inet_ntop( AF_INET, &rin.sin_addr, str, sizeof( str ) ),
ntohs( rin.sin_port ), buf );
// just convert the characters to upper case
len = strlen( buf );
for ( i = 0; i < len; i++ )
buf[i] = toupper( buf[i] );
n = sendto( sock_fd, buf, len + 1, 0, ( struct sockaddr * ) &rin,
address_size );
if ( n == -1 )
{
perror( "call to sendto.\n" );
exit( 1 );
}
}
}
