UNIXNetworkStreamReader

UNIXNetworkStreamReader Class

UNIXNetworkStreamReader objects receive data using UNIX domain sockets on a single machine. The class defines methods to create a connection and check the connection for incoming data, and read any data for the application.

Here are slightly abreviated versions of the sockread.c and sockwrite.c example programs. This is the source code of sockread.c.

int main () {
  UNIXNetworkStreamReader new reader;
  SystemErrnoException new ex;
  FileStream new f;
  String new sockName;
  String new data;

  sockName = "testsocket";

  reader makeSocketPath sockName;
  printf ("reader socket:  %s\n", reader socketPath);

  /* Delete a socket from a previous connection if necessary. */
  if (f exists reader socketPath) {
    f deleteFile reader socketPath;
  }

  reader open;
  if (ex pending) {
    ex handle;
    unlink (reader socketPath);
    return -1;
  }

  while (1) {
    data = reader sockRead;

    if (data length > 0) {
      printf ("%s\n", data);
    }
    if (ex pending) {
      ex handle;
      break;
    }
    usleep (1000);
  }

  return 0;
}

And here is sockwrite.c. For details about its operation, refer to the UNIXNetworkStreamWriter section. See UNIXNetworkStreamWriter.

int main (int argc, char **argv) {
  UNIXNetworkStreamWriter new writer;
  SystemErrnoException new ex;
  String new sockName;
  String new data;

  sockName = "testsocket";

  writer makeSocketPath sockName;
  printf ("writer socket:  %s\n", writer socketPath);

  writer open;
  if (ex pending) {
    ex handle;
  }

  writer sockWrite argv[1];

  if (ex pending) {
    ex handle;
  }

  exit (0);
}

The programs communicate if started from different shells used by different virtual terminals or different windows on a graphical desktop, or if the reader program is started in the background and the writer started in the foreground.

Instance Variables

charsRead

An Integer that contains the number of characters read by the last reception of data from a connection, or zero if there is no data waiting. Refer to the method sockRead, below.

Instance Methods

open (void)

Creates a socket to read data from the socket name by the receiver’s socketPath instance variable, which is defined in UNIXNetworkStream class. See UNIXNetworkStream.

The method returns the file number of the socket, or -1 if there is an error, and raises a SystemErrnoException if an error occurred in the network library routines.

openOn (String socketpath)

Creates a new reader socket and binds it to socketpath. Sets the receiver’s socketPath instance variable to the argument. Returns an Integer with the file number of the newly created socket.

sockRead (void)

Returns a String containing data received from the socket previously created by the open method, above, and sets the charsRead instance variable to the number of characters read.

If no data is waiting, the method returns an empty string and sets the receiver’s charsRead instance variable to 0.

If an error occurs during one of the system calls, the method raises a SystemErrnoException.