simple network in C from CS283

client.c

#include "csapp.h" 

/* usage: ./echoclient host port */
int main(int argc, char **argv)
{ 
	int clientfd, port; 
	char *host, buf[MAXLINE]; 
	rio_t rio; 
	host = argv[1];
	port = atoi(argv[2]); 
	clientfd = Open_clientfd(host, port);
	Rio_readinitb(&rio, clientfd); 
	printf("Enter message:"); fflush(stdout);
	while (Fgets(buf, MAXLINE, stdin) !=
			NULL) { 
		Rio_writen(clientfd, buf, strlen(buf)); 
		Rio_readlineb(&rio, buf, MAXLINE); 
		printf("Echo:");
		Fputs(buf, stdout); 
		printf("Enter message:");
		fflush(stdout);
	} 
	Close(clientfd); 
	exit(0); 
}

server.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "csapp.c"

void echo(int connfd)
{
    size_t n;
    char buf[MAXLINE];
    rio_t rio;

    Rio_readinitb(&rio, connfd);
    while((n = Rio_readlineb(&rio, buf, MAXLINE)) != 0) {
        //upper_case(buf);
        Rio_writen(connfd, buf, n);
        printf("server received bytes\n");
    }
}


int main(int argc, char **argv) {
    int listenfd, connfd, port, clientlen;
    struct sockaddr_in clientaddr;
    struct hostent *hp;
    char *haddrp;

    port = atoi(argv[1]); /* the server listens on a port passed 
                             on the command line */
    listenfd = open_listenfd(port); 

    while (1) {
        clientlen = sizeof(clientaddr); 
        connfd = Accept(listenfd, (SA *)&clientaddr, &clientlen);
        hp = Gethostbyaddr((const char *)&clientaddr.sin_addr.s_addr,
                sizeof(clientaddr.sin_addr.s_addr), AF_INET);
        haddrp = inet_ntoa(clientaddr.sin_addr);
        printf("server connected to %s (%s)\n", hp->h_name, haddrp);
        echo(connfd);
        Close(connfd);
    }
}