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

#define RCVBUFSIZE 32   /* Size of receive buffer */

void DieWithError(char *errorMessage);  /* Error handling function */

int main(int argc, char *argv[])
{
   int sock;                        /* Socket descriptor */
   struct sockaddr_in echoServAddr; /* Echo server address */
   struct hostent *thehost;         /* Hostent from gethostbyname() */
   unsigned short echoServPort;     /* Echo server port */
   char *servIP;                    /* Server IP address (dotted quad) */
   char *echoString;                /* String to send to echo server */
   char echoBuffer[RCVBUFSIZE];     /* Buffer for echo string */
   unsigned int echoStringLen;      /* Length of string to echo */
   int bytesRcvd, totalBytesRcvd;   /* Bytes read in single recv()
                                       and total bytes read */

   if ((argc < 2) || (argc > 3))    /* Test for correct number of arguments */
   {
      fprintf(stderr, "Usage: %s <Server IP>  [<Echo Port>]\n",
              argv[0]);
      exit(1);
   }

   servIP = argv[1];             /* First arg: server IP address (dotted quad) */

   if (argc == 3)
       echoServPort = atoi(argv[2]); /* Use given port, if any */
   else
       echoServPort = 7;  /* 7 is the well-known port for the echo service */

   printf("Connecting to Server: %s at Port: %d...\n", servIP, echoServPort);


   while(1) { // INFINITE WHILE

       printf("%s", "Enter a string (Press CTRL+C to quit): ");
       scanf("%s", echoString);

       /* Create a reliable, stream socket using TCP */
       if ((sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
           DieWithError("socket() failed");

       printf("Sent to TCP Server: %s\n", echoString);

       /* Construct the server address structure */
       memset(&echoServAddr, 0, sizeof(echoServAddr));     /* Zero out structure */
       echoServAddr.sin_family      = AF_INET;             /* Internet address family */
       echoServAddr.sin_addr.s_addr = inet_addr(servIP);   /* Server IP address */
       echoServAddr.sin_port        = htons(echoServPort); /* Server port */

       /* If user gave a dotted decimal address, we need to resolve it  */
       if (echoServAddr.sin_addr.s_addr == -1) {
            thehost = gethostbyname(servIP);
            echoServAddr.sin_addr.s_addr = *((unsigned long *) thehost->h_addr_list[0]);
       }


       /* Establish the connection to the echo server */
       if (connect(sock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr)) < 0)
           DieWithError("connect() failed");

       echoStringLen = strlen(echoString);          /* Determine input length */

       /* Send the string to the server */
       if (send(sock, echoString, echoStringLen, 0) != echoStringLen)
           DieWithError("send() sent a different number of bytes than expected");

       /* Receive the same string back from the server */
       totalBytesRcvd = 0;
       printf("Received from TCP Server: ");                /* Setup to print the echoed string */
       while (totalBytesRcvd < echoStringLen) {
          /* Receive up to the buffer size (minus 1 to leave space for
             a null terminator) bytes from the sender */
          if ((bytesRcvd = recv(sock, echoBuffer, RCVBUFSIZE - 1, 0)) <= 0)
              DieWithError("recv() failed or connection closed prematurely");
          totalBytesRcvd += bytesRcvd;   /* Keep tally of total bytes */
          echoBuffer[bytesRcvd] = '\0';  /* Terminate the string! */
          printf(echoBuffer);            /* Print the echo buffer */
       }

       printf("\n");    /* Print a final linefeed */

       close(sock);

   } // End infinite while loop

   exit(0);
}