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| 客户端
# include <sys/socket.h>
# include <netdb.h>
# include <stdio.h>
# include <stdlib.h>
# include <string.h>
# include <unistd.h>
# include <arpa/inet.h> //inet_addr
# define SERVERPORT 9999
# define LOCALHOST "127.0.0.1"
# define MYMSGLEN 2048
void question ( int sock, char * msg, struct sockaddr_in * addr, struct sockaddr_in * from )
{
int code, length, ret ;
socklen_t len;
// Send the length of the string.
length = strlen ( msg ) ; // + 1 ;
// Send the string of characters.
len = sizeof ( struct sockaddr_in ) ;
code = sendto ( sock, msg, length, 0, ( struct sockaddr * ) addr, len ) ;
if ( code == -1 ) {
perror ( "sendto" ) ;
close ( sock ) ;
exit ( 1 ) ;
}
// Wait for the answer.
memset ( msg, 0, length ) ;
len = sizeof ( * from ) ;
code = recvfrom ( sock, ( char * ) msg, length, 0, ( struct sockaddr * ) from, & len ) ;
if ( code == -1 ) {
perror ( "recvfrom" ) ;
close ( sock ) ;
exit ( 1 ) ;
}
// Empty message!!!! 0 value returned in UDP mode does not mean closing a connection since there is no connection
// We release the resource and exit the program anyway
if ( code == 0 )
{
// Release ressources.
code = close ( sock ) ;
if ( code == -1 ) {
perror ( "close" ) ;
}
exit ( 1 ) ;
}
}
int main ( int argc, char * argv [ ] )
{
int item ;
socklen_t len;
// Ask for the string of characters.
char string [ MYMSGLEN ] ;
// Create UDP socket and init server address structure.
int sock ;
sock = socket ( AF_INET, SOCK_DGRAM, 0 ) ;
if ( sock == -1 ) {
perror ( "socket" ) ;
exit ( 1 ) ;
}
// Initialisation of the sockaddr_in data structure
struct sockaddr_in addr ;
memset ( & addr, 0, sizeof ( struct sockaddr_in ) ) ;
addr . sin_family = AF_INET ;
addr . sin_port = htons ( SERVERPORT ) ;
addr . sin_addr . s_addr = inet_addr ( LOCALHOST ) ;
while ( 1 )
{
memset ( string, 0, sizeof( string ) ) ;
printf ( "\n----------------------------------------------------------------------\n" ) ;
printf ( "Please type a message to transfer for processing:" ) ;
item = scanf ( "%[^\n]%*c", string ) ; //reads a hole line till a new line feed
//This is in case of empty message
if ( item == 0 )
{
scanf("%*c");
continue;
}
printf ( "The message being sent is: '%s' \n", string ) ;
printf( "----------------------------------------------------------------------\n" ) ;
if ( !memcmp ( "quit#", string, 5 ) )
{
printf ( " Client exiting upon user request \n" ) ;
close ( sock ) ;
exit ( 1 ) ;
}
// Ask the question and wait for the answer.
struct sockaddr_in from ;
question ( sock, string, & addr, & from ) ;
// Display the result.
printf ( "\n----------------------------------------------------------------------\n" ) ;
printf ( "The processed message is received from server %s, with port number: %d \n" , inet_ntoa( from.sin_addr ), ntohs( from.sin_port ) ) ;
printf ( "The message is : %s\n", string ) ;
printf ( "----------------------------------------------------------------------\n" ) ;
}
return ( 0 ) ;
}
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