## Choosing a Port

Even fancier than always using the UID is to default to our UID as a
port, but allow choosing an alternative port on the command line,
which we will take advantage of when we get to CAS:

```python
    import sys, os
    if len(sys.argv) > 1:
        # arg, if any, is the desired port number
        port = int(sys.argv[1])
        assert(port>1024)
    else:
        port = os.getuid()
    app.debug = True
    app.run('0.0.0.0',port)
```

You can mostly ignore this code and just use it as boilerplate, but if
you don't understand it and want some help, contact me.