/*
NAME : server.C
TYPE : C++ SOURCE
AUTHOR : Arunkumar Elango
DESCRIPTION : 
This file contains the source code for the server. It takes the following command line as input :

					$ server [-p portnumber]

It creates and binds a socket at the either the well known portnumber or at the portnumber given in the 
commandline. Then, it waits for a connection request from a client. When the request arrives, it reads the 
socket, to get the string to be echoed. It then writes out this same string with a "Server echo : " prefix, 
back to the socket.
*/

#include <iostream.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
//#include <fcntl.h>
#include <memory.h>
#include <string.h>
#include <errno.h>
#include <sys/errno.h>
//#include <sys/wait.h>


const int MAXSTR=1024;		// Maximum String length
const long PORTNUM=54715;	// The "Well-known" port number
//const int PASSWORD = 21;	// The password that the server expects.

void handleRequest(int);	// Function to handle clients' request(s)
//int numberChildren;		// The current number of child processes.
//void childExit(int);		// signal handler for SIGCHLD

main( int argc, char *argv[])
{
int portNumber;
//char executableName[MAXSTR];
//struct sigaction action;
	
	// Validate and read from the command line
	if ( (argc != 3) && (argc != 1) )
	{
		cerr << "Invalid command line.\n";
		exit(1);
	}
	if ( argc == 1 )
	{
		portNumber = PORTNUM;
	}
	else 
	{
		if (!strcmp(argv[1],"-p"))
		{
			portNumber = atoi(argv[2]);
		}
		else
		{
			cerr << "Invalid command line.\n";
			exit(1);
		}
	}

	if (portNumber < 10000)
	{
		cerr << "Port number has to be atleast 10000.\n";
		exit(1);
	}
	
	// At this point, the command line has been validated.

int sockfd,newsockfd,clilen,childpid;
struct sockaddr_in serv_addr,cli_addr;

	// Create a new TCP socket...
	if ((sockfd = socket(AF_INET,SOCK_STREAM,0)) < 0)
	{
		cerr << "Cant open stream socket.\n";
		exit(0);
	}

	bzero((char *)&serv_addr,sizeof(serv_addr)) ;

	serv_addr.sin_family = AF_INET;
	serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
	serv_addr.sin_port = htons(portNumber);

	// Bind the socket to the server's ( this process ) address.
	if (bind(sockfd,(struct sockaddr *)&serv_addr,sizeof(serv_addr)) < 0)
	{
		cerr << "Cant bind local address.\n";
		exit(1);
	}
	
	// Listen for connections in this socket
	listen(sockfd,5);
int status;
	cerr <<  " Connected to port : " << portNumber << "\n";

char buf[MAXSTR],ack[MAXSTR];
	
	// repeat forever..
	while (1)
	{
		clilen = sizeof(cli_addr);
		// Accept a client's request, and get the client's address info into the local variable cli_addr.
		newsockfd = accept(sockfd,(struct sockaddr *)&cli_addr,&clilen);
		// After accepting the connection, all transaction with this client would happen with the new socket descriptor - newsockfd.

		if ((newsockfd < 0) &&  (errno != EINTR))
			cerr << " server : accept error.\n";
		else if (newsockfd > 0)
		{
			handleRequest(newsockfd);
			close(newsockfd);
		}
	}

}


void handleRequest(int newsockfd) 
{
char buf[MAXSTR],execName[MAXSTR],ack[MAXSTR];
char data[MAXSTR];

	// Read from the socket, for the password and the requested command.
	read(newsockfd,(void *)buf,MAXSTR);
	sscanf(buf,"%s\n",execName);

	sprintf(ack,"Server echo : %s",execName);
	cout << "From client: " << execName << endl;

	// Write back the response to the socket
	write(newsockfd,ack,strlen(ack));
}