#include <stdio.h>

#include <stdlib.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <string.h>

#include <netinet/in.h>

#define MAXLINE 80

#define SERV_PORT 8888

void do_echo( int sockfd, struct sockaddr *pcliaddr, socklen_t client )

{

    int n;

    socklen_t len;

    char mesg[];

    while ()

    {

        len = client;

        n = recvfrom( sockfd, mesg, , , pcliaddr, &len );

        sendto( sockfd, mesg, n, , pcliaddr, len );

        mesg[n] = ;

        fputs( mesg, stdout );

    }

    return;

}

int main( void )

{

    int sockfd;

    struct sockaddr_in servaddr, cliaddr;

    sockfd = socket( AF_INET, SOCK_DGRAM,  );

    bzero( &servaddr, sizeof(servaddr) );

    servaddr.sin_family = AF_INET;

    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);

    servaddr.sin_port = htons(SERV_PORT);

    if ( bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == - )

    {

        perror("bind error");

        exit();

    }

    do_echo( sockfd, (struct sockaddr *)&cliaddr, sizeof(cliaddr) );

    return ;

}

#include <stdio.h>

#include <stdlib.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <string.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <unistd.h>

#define MAXLINE 80

#define SERV_PORT 8888

void do_cli( FILE *fp, int sockfd, struct sockaddr *pservaddr, socklen_t servlen )

{

    int n;

    char sendline[MAXLINE], recvline[MAXLINE + ];

    if ( connect( sockfd, (struct sockaddr *)pservaddr, servlen ) == - )

    {

        perror("connect error");

        exit();

    }

    while ( fgets(sendline, MAXLINE, fp ) != NULL )

    {

        write( sockfd, sendline, strlen(sendline) );

        n = read( sockfd, recvline, MAXLINE );

        if ( n == - )

        {

            perror("read error");

            exit();

        }

        recvline[n] = ;

        fputs( recvline, stdout );

    }

    return;

}

int main( int argc, char **argv )

{

    int sockfd;

    struct sockaddr_in servaddr;

    if ( argc !=  )

    {

        printf("usage: udpclient <IPaddress>\n");

        exit();

    }

    bzero( &servaddr, sizeof(servaddr) );

    servaddr.sin_family = AF_INET;

    servaddr.sin_port = htons(SERV_PORT);

    if ( inet_pton(AF_INET, argv[], &servaddr.sin_addr ) <=  )

    {

        printf("[%s] is not a valid IPaddress\n", argv[]);

        exit();

    }

    sockfd = socket(AF_INET, SOCK_DGRAM,  );

    do_cli( stdin, sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr) );

    return ;

}