/* myserver.c */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <ctype.h>

#define SERV_PORT 6666
#define SERV_IP  INADDR_ANY
#define MAXLISTENQ 128

void perr_exit(const char * s)
{
	perror(s);
	exit(1);
}

int main(void)
{
	int listenfd, connfd;
	int n;
	char buf[BUFSIZ] ,clieIP[BUFSIZ];
	struct sockaddr_in servaddr, clieaddr;
	socklen_t clieaddr_len;

	// create socket
	if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1 ) {
		perr_exit("socket error");
	}

	 // bind socket address
	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_port = htons(SERV_PORT);
	servaddr.sin_addr.s_addr = htonl(SERV_IP);

	if((n = bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr))) == -1) {
				perr_exit("bind error");
	}

	 // monitor
	if ((n = listen(listenfd, MAXLISTENQ)) == -1) {
		perr_exit("listen error");
	}

	printf("wait for client connect ...\n");

	clieaddr_len = sizeof(clieaddr);
	if ((connfd = accept(listenfd, (struct sockaddr *)&clieaddr, &clieaddr_len)) == -1) {
		perr_exit("accept error");
	}
	
	 // Display the client's IP address
	if (inet_ntop(AF_INET, &clieaddr.sin_addr.s_addr, clieIP, sizeof(clieIP)) == NULL) {
		perr_exit("inet_ntop error");
	}
	printf("connected---> client IP address: %s\tport: %d\t\n", clieIP, ntohs(clieaddr.sin_port));
	
	while (1) {
		 // Read information from the client
		if ((n = read(connfd, &buf, sizeof(buf))) == -1) {
			perr_exit("read error");
		}
		 // print to standard output
		write(STDOUT_FILENO, buf, n);

		for (int i = 0; i < n; i++) {
			buf[i] = toupper(buf[i]);
		}
		 // Send information to the client
		if ((n = write(connfd, buf, n)) == -1) {
			perr_exit("write to client error");
		}
	}
	return 0;
}