#include <stdio.h>      /* for printf() and fprintf() */
#include <sys/socket.h> /* for socket(), bind(), and connect() */
#include <arpa/inet.h>  /* for sockaddr_in and inet_ntoa() */
#include <stdlib.h>     /* for atoi() and exit() */
#include <string.h>     /* for memset() */
#include <unistd.h>     /* for close() */

#define MAXPENDING 5    /* Maximum outstanding connection requests */
#define RCVBUFSIZE 32

int main()
{
    int servSock;                    /* Socket descriptor for server */
    int clntSock;                    /* Socket descriptor for client */
    struct sockaddr_in echoServAddr; /* Local address */
    struct sockaddr_in echoClntAddr; /* Client address */
    unsigned short echoServPort;     /* Server port */
    unsigned int clntLen;            /* Length of client address data structure */
    char echoBuffer[RCVBUFSIZE];        /* Buffer for echo string */
    int recvMsgSize;                    /* Size of received message */


    echoServPort = 2000;  /* First arg:  local port */

    /* Create socket for incoming connections */
    if ((servSock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
    {
		perror("socket() failed");
		exit(1);
    }
      
    /* Construct local address structure */
    memset(&echoServAddr, 0, sizeof(echoServAddr));   /* Zero out structure */
    echoServAddr.sin_family = AF_INET;                /* Internet address family */
    echoServAddr.sin_addr.s_addr = htonl(INADDR_ANY); /* Any incoming interface */
    echoServAddr.sin_port = htons(echoServPort);      /* Local port */

    /* Bind to the local address */
    if (bind(servSock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr)) < 0)
    {
		perror("bind() failed");
		exit(1);
    }

    /* Mark the socket so it will listen for incoming connections */
    if (listen(servSock, MAXPENDING) < 0)
    {
		perror("listen() failed");
		exit(1);
    }

    for (;;) /* Run forever */
    {
        /* Set the size of the in-out parameter */
        clntLen = sizeof(echoClntAddr);

        /* Wait for a client to connect */
        if ((clntSock = accept(servSock, (struct sockaddr *) &echoClntAddr, 
                               &clntLen)) < 0)
    	{
			perror("accept() failed");
			exit(1);
    	}

        /* clntSock is connected to a client! */

        printf("Handling client %s\n", inet_ntoa(echoClntAddr.sin_addr));


    	/* Receive message from client */
    	if ((recvMsgSize = recv(clntSock, echoBuffer, RCVBUFSIZE, 0)) < 0)
    	{
			perror("recv() failed");
			exit(1);
    	}

    	/* Send received string and receive again until end of transmission */
    	while (recvMsgSize > 0)      /* zero indicates end of transmission */
    	{
        	/* Echo message back to client */
        	if (send(clntSock, echoBuffer, recvMsgSize, 0) != recvMsgSize)
	    	{
				perror("send() failed");
				exit(1);
	    	}

			/* See if there is more data to receive */
			if ((recvMsgSize = recv(clntSock, echoBuffer, RCVBUFSIZE, 0)) < 0)
	    	{
				perror("recv() failed");
				exit(1);
    		}
    	}

    	close(clntSock);    /* Close client socket */

    }
    /* NOT REACHED */
}