Linux 網絡編程---->簡單的UDP實例

這是一個簡單的UDP的實例而已～

//!> server
//!> server.c




#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <netinet/in.h>

#define SERV_PORT 6000
#define MAXLINE 1024

int main( int argc, char ** argv )
{
char recv[MAXLINE];
int listenfd,connfd;
int chilen, len,i;
int nread;
structsockaddr_in servaddr, chiaddr;

//!> establish the socket
//!>
if( (listenfd = socket( AF_INET, SOCK_DGRAM,0 ) ) == -1 )
{
printf("Socket error.. %d\n", errno);
exit(EXIT_FAILURE );
}

//!>
//!> write info
bzero(&servaddr, sizeof( servaddr ) );
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr =htonl( INADDR_ANY);
servaddr.sin_port = htons( SERV_PORT );

//!>
//!> bind
if( bind(listenfd, ( struct sockaddr * )&servaddr, sizeof(servaddr ) ) == -1 )
{
printf("Binderror... %d\n", errno);
exit(EXIT_FAILURE );
}

while( 1)
{
chilen =sizeof( chiaddr );

memset( recv, 0, sizeof( recv ) );
nread =recvfrom(connfd,recv, MAXLINE, 0, (struct sockaddr*)&chiaddr, &chilen);//read(connfd, recv, MAXLINE );
//!> 記住：一般都用它
if( nread ==-1 )
{
continue;
printf("Readerror ... %d\n", errno);
close(connfd );
exit(EXIT_FAILURE );
}
else if(nread == 0 )
{
printf("Haveno data..\n");
continue; //!> return
}
else
{
len =sizeof( recv );
recv[len] ='\0';
printf("Server get from client : %s\n", recv);

i = 0;
while(recv[i] ) //!> 此處是一個簡單的處理，將小寫字母改成大寫回送
{
recv[i] =toupper( recv[i] );
i++;
}

sendto(connfd, recv, strlen( recv ), 0, (struct sockaddr*)&chiaddr, chilen);
//!> send to client
}

}

return0;
}


//!> client
//!>client.c




#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <netinet/in.h>

#define SERV_PORT 6000
#define MAXLINE 1024

int main( int argc, char ** argv )
{
char recv[MAXLINE];
int connfd;
int nread;
int len;
structsockaddr_in servaddr;

if( argc !=2 )
{
printf("Please input the server's IP only !");
exit(EXIT_FAILURE );
}

//!>
//!> socket
if( ( connfd= socket( AF_INET, SOCK_DGRAM,0 ) ) == -1 )
{
printf("Socket error.. %d\n", errno);
exit(EXIT_FAILURE );
}

//!>
//!> info
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERV_PORT);
inet_pton(AF_INET, argv[1] ,&servaddr.sin_addr);


while( 1)
{

//write(connfd, "hello\n", 7 );

memset(recv, 0, sizeof( recv ) );
sendto(connfd, "hello\n", 7, 0, (struct sockaddr*)&servaddr, sizeof(servaddr));
printf("Client send : hello\n");

sleep( 2);

len =sizeof( servaddr );
nread =recvfrom(connfd, recv, MAXLINE, 0, (struct sockaddr*)&servaddr, &len);//read( connfd,recv, MAXLINE );

if( nread ==-1 )
{
printf("Readerror.. %d\n", errno);
exit(EXIT_FAILURE );
}
else if(nread == 0 )
{
continue;
}
else
{
len =strlen( recv );
recv[len] ='\0';
printf("Client get from server : %s\n", recv);
}

}

close(connfd );

return0;
}