Our first network client!

• Intentionally easy!
  • The full program file is right here
  • The protocol—informally, the set of rules both client and server must follow if they're to speak with one another—is simple.
  • The protocol here is...
    • The client connects (e.g. "rings" the service's phone at a particular "extension", and waits for the server to "pick up")
    • The client says nothing.
    • The server speaks by publishing the current time into its own end of the connection and then hangs up.
    • The client ingests the published text (understood, by protocol, to be just one line), publishes it to the console, and then itself hangs up.

  int main(int argc, char *argv[]) {
    int clientSocket = createClientSocket("myth7.stanford.edu", 12345);
    if (clientSocket == kClientSocketError) {
      cerr << "Time server could not be reached" << endl;
      cerr << "Aborting" << endl;
      return 1;
    }
    sockbuf sb(clientSocket);
    iosockstream ss(&sb);
    string timeline;
    getline(ss, timeline);
    cout << timeline << endl;
    return 0;
  }

  • We'll discuss the implementation of createClientSocket on Monday, but it's okay to just view it as a built-in that sets up a bidirectional pipe between the client and the server running on the specified host and port number.