#include <sys/types.h>

#include <sys/socket.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <ctype.h>

#include <unistd.h>

#define SOCK_PORT 49128

#define MAXLINE 80

int main()

{

    int sockfd, connfd;

    struct sockaddr_in servaddr, cliaddr;

    socklen_t cliaddr_len;

    char buf[MAXLINE];

    char str[INET_ADDRSTRLEN];

    int i, n;    

    if((sockfd = socket(AF_INET, SOCK_STREAM, )) < ) {

        perror("socket");

        exit();

    }

    /*Construct sockaddr_in struct*/

    bzero(&servaddr, sizeof(servaddr));

    servaddr.sin_family = AF_INET;

    servaddr.sin_port = htons(SOCK_PORT);

    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);

    if (bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) < ) {

        perror("connect");

        exit();

    }

    if (listen(sockfd, ) < ) {

        perror("listen");

        exit();

    }

    while () {

        cliaddr_len = sizeof(cliaddr);

        connfd = accept(sockfd, (struct sockaddr *)&cliaddr, &cliaddr_len);

        n = read(connfd, buf, MAXLINE);

        printf("received from %s at PORT %d\n", inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)),

            ntohs(cliaddr.sin_port));

        for (i = ; i < n; i++)

            buf[i] = toupper(buf[i]);

        write(connfd, buf, n);

        close(connfd);

    }

    close(sockfd);

    return ;

}

#include <sys/socket.h>

#include <sys/types.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <arpa/inet.h>

#include <unistd.h>

#include <stdio.h>

#include <string.h>

#define SERV_PORT 49128

#define MAXLINE 80

int main(int argc, char *argv[])

{

    int sockfd, n;

    struct sockaddr_in servaddr;

    char *str;

    char buf[MAXLINE];

    if (argc != ) {

        fputs("usage: ./client message\n", stderr);

        exit();

    }

    str = argv[];

    if ((sockfd = socket(AF_INET, SOCK_STREAM, )) < ) {

        perror("socket");

        exit();

    }

    bzero(&servaddr, sizeof(servaddr));

    servaddr.sin_family = AF_INET;

    inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);

    servaddr.sin_port = htons(SERV_PORT);    

    connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));

    write(sockfd, str, strlen(str));

    n = read(sockfd, buf, MAXLINE);

    printf("Response from server:\n");

    write(STDOUT_FILENO, buf, n);

    close(sockfd);

    return ;

}