TCPEchoClient.cpp

#include <iostream>

#include <errno.h>
#include <fcntl.h>
#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 <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 */
    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 < 3) || (argc > 4))    /* Test for correct number of arguments */
    {
       fprintf(stderr, "Usage: %s <Server IP> <Echo Word> [<Echo Port>]\n",
               argv[0]);
       exit(1);
    }

    servIP = argv[1];             /* First arg: server IP address (dotted quad) */
    //echoString = argv[2];         /* Second arg: string to echo */
    echoString = "000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000";         /* Second arg: string to echo */

    if (argc == 4)
        echoServPort = atoi(argv[3]); /* Use given port, if any */
    else
        echoServPort = 7;  /* 7 is the well-known port for the echo service */

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

    /* 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 */

    /* 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 */

    // NON BLOCKING!
    int flags = fcntl (sock, F_GETFL, 0 );
    fcntl (sock, F_SETFL, flags | O_NONBLOCK );
    
    


    /* Send the string to the server. */
    int sent = 0;
    do
    {
      std::cout << "Send?" << std::endl; 
      if ((sent = send(sock, echoString, echoStringLen, 0)) == -1)
      {
        const int errNumber = errno;
        if (errNumber == EWOULDBLOCK || errNumber == EAGAIN)
	{
          std::cout << "First slow consuming here: [" << sent << "]" << std::endl;
   	  break;
	}
      }
      std::cout << "Sent! [" << sent << "]." << std::endl;
    }
    while (true);

    // SELECT
    int servSock[1];                   /* Socket descriptors for server */
    servSock[0] = sock;
    int maxDescriptor = echoServPort;               /* Maximum socket descriptor value */
    fd_set sockSet;                  /* Set of socket descriptors for select() */
    long timeout = 1;                    /* Timeout value given on command-line */
    struct timeval selTimeout;       /* Timeout for select() */
    int running = 1;                 /* 1 if server should be running; 0 otherwise */
    int noPorts = 1;                     /* Number of port specified on command-line */
    int port;                        /* Looping variable for ports */
    unsigned short portNo;           /* Actual port number */

    while (running)
    {
        /* Zero socket descriptor vector and set for server sockets */
        /* This must be reset every time select() is called */
        FD_ZERO(&sockSet);
        /* Add socket to descriptor vector */
        FD_SET(sock, &sockSet);

        /* Timeout specification */
        /* This must be reset every time select() is called */
        selTimeout.tv_sec = timeout;       /* timeout (secs.) */
        selTimeout.tv_usec = 0;            /* 0 microseconds */

        /* Suspend program until descriptor is ready or timeout */
        if (select(maxDescriptor + 1, NULL, &sockSet, NULL, &selTimeout) == 0)
            printf("No echo requests for %ld secs...Server still alive\n", timeout);
        else 
        {
            if (FD_ISSET(sock, &sockSet)) /* Ready for write !!*/
            {
                printf("Ready for write!!!!!! \n");
//                running = 0;
               if ((sent = send(sock, echoString, echoStringLen, 0)) == -1)
               {
                 const int errNumber = errno;
                if (errNumber == EWOULDBLOCK || errNumber == EAGAIN)
                {
                   std::cout << "Slow consuming here: [" << sent << "]" << std::endl;
  	        }
	      }
	      else
	      {
                 std::cout << "Sent! [" << sent << "]." << std::endl;
	      }
	   }
      }
    }


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

    close(sock);
    exit(0);
}


void DieWithError(char *errorMessage)
{
    perror(errorMessage);
    exit(1);
}

int AcceptTCPConnection(int servSock)
{
    int clntSock;                    /* Socket descriptor for client */
    struct sockaddr_in echoClntAddr; /* Client address */
    unsigned int clntLen;            /* Length of client address data structure */

    /* 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)
        DieWithError("accept() failed");
    
    /* clntSock is connected to a client! */
    
    printf("Handling client %s\n", inet_ntoa(echoClntAddr.sin_addr));

    return clntSock;
}