source: tools/SkyQualityMonitor/sqm.cpp@ 108

/********************************************************************\

  Interface to the sky quality monitor (essentially a socket interface)
  
  Writes slow data at given rate. Terminate with CTRL-c.
  
  Oliver Grimm, July 2009

\********************************************************************/

#include <stdlib.h>
#include <string.h>
#include <iostream>
#include <sys/socket.h>
#include <netdb.h>
#include <signal.h>

#include "../../drsdaq/SlowData.h"

#define PERIOD 10       // Measurement period (integer)
#define READ_CMD "rx"   // Command to read from device
#define BUF_SIZE 1000   // Read buffer size

int SocketDescriptor;   // Global to be accessible by exit handler
SlowData *SlowDataClass;

// Close socket descriptor when CTRL-c pressed
void ExitHandler(int Signal) {
  if (!close(SocketDescriptor)) printf("Connection closed.\n");
  delete SlowDataClass;
  exit(EXIT_SUCCESS);
}

// Main program
int main(int argc, char *argv[]) {
        
  char Buffer[BUF_SIZE],ServerName[BUF_SIZE]="sqm.ethz.ch";
  char SlowDir[BUF_SIZE]="/ct3data/SlowData";
  int DAQPort = 10001, Period = PERIOD;
  struct sockaddr_in SocketAddress;
  fd_set ReadFileDescriptor;
  time_t Time;
  
  if (argc != 5) {
    printf("+++ Sky Quality Monitor Interface +++\n");
    printf("Usage: %s <server name> <port> <slow data dir> <period (sec)>\n", argv[0]);
    printf("Taking defaults: <%s> <%d> <%s> <%d>\n", ServerName, DAQPort, SlowDir, Period);
  } 
  else {
    snprintf(ServerName, sizeof(ServerName), argv[1]);
    snprintf(SlowDir, sizeof(SlowDir), argv[3]);
    DAQPort = atoi(argv[2]);
    Period = atoi(argv[4]);
  }
  
  // Open socket descriptor
  if ((SocketDescriptor = socket(PF_INET, SOCK_STREAM, 0)) == -1) {
    printf("Error: Could not open socket.");
    exit(EXIT_FAILURE);
  }
    
  // Resolve hostname and try to connect to server
  struct hostent *hostent = gethostbyname(ServerName);
  if (hostent==0) {
    printf("\nCould not resolve host name.\n");
    close(SocketDescriptor);
    exit(EXIT_FAILURE);
  }

  SocketAddress.sin_family = PF_INET;
  SocketAddress.sin_port = htons((unsigned short) DAQPort);
  SocketAddress.sin_addr = *(struct in_addr*) hostent->h_addr;
  
  if (connect(SocketDescriptor, (struct sockaddr *) &SocketAddress, sizeof(SocketAddress))==-1) {
    printf("Error: Could not connect to server %s (port %d)\n", ServerName, DAQPort);
    close(SocketDescriptor);
    exit(EXIT_FAILURE);
  }
  printf("\nConnected to %s (port %d)\n", ServerName, DAQPort);
  signal(SIGPIPE,SIG_IGN);  // Do not kill process if writing to closed socket
  signal(SIGINT, &ExitHandler);

  // Create instance of slow data class for monitoring data
  SlowDataClass = new SlowData("SQM", SlowDir);
  if(SlowDataClass->ErrorCode != 0) {
    printf("Error: Could not open slow data file in %s (%s)\n", SlowDir, strerror(SlowDataClass->ErrorCode));
    exit(EXIT_FAILURE);
  }
  SlowDataClass->NewEntry("Data-Info", "Data string as returned by sqm. Commata and the letter 'm' are replaced by whitespaces");

  while(true) {
    // Write read command to socket
    if ((write(SocketDescriptor, READ_CMD, strlen(READ_CMD)))<1) { 
      printf("Error: Could not write read command to socket.\n");
    }
    usleep((int) (Period*1e6/2));  // Wait half period here to allow for response
    
    // Wait for data from socket with time-out
    FD_ZERO(&ReadFileDescriptor);   
    FD_SET(SocketDescriptor, &ReadFileDescriptor);
    struct timeval WaitTime = {Period, 0};
    if (select(((int) SocketDescriptor)+1, &ReadFileDescriptor, NULL, NULL, &WaitTime)==-1) {
      perror("Error with select()");
      break;
    }

    if (!FD_ISSET(SocketDescriptor, &ReadFileDescriptor)) { 
      printf("Time-out of %d seconds expired before receiving response from socket.\n", PERIOD);
      continue;
    }

    memset(Buffer, 0, BUF_SIZE);
    if(read(SocketDescriptor, Buffer, BUF_SIZE)==0) {
      printf("Server not existing anymore, exiting...\n");
      break;
    }

    // Remove letters and commata from string before writing as slow data
    for (int i=0; i<strlen(Buffer); i++) {
      if (Buffer[i]=='m' || Buffer[i]==',' || iscntrl(Buffer[i])) Buffer[i] = ' ';
    }
    SlowDataClass->NewEntry("Data", Buffer);
    if(SlowDataClass->ErrorCode != 0) {
      printf("Error: Could not write to slow data file (%s)\n", strerror(SlowDataClass->ErrorCode));
      break;
    }
    Time = time(NULL);
    printf("\r%s %s CTRL-c to exit.",Buffer, asctime(localtime(&Time)));
    fflush(stdout);
    usleep((int) (Period*1e6/2)); // Wait second half period here
 
  } // while()
  
  ExitHandler(0);
}