codec@codec-System-Product-Name:~$ ryu-manager
loading app ryu.controller.ofp_handler
instantiating app ryu.controller.ofp_handler of OFPHandler
hub: uncaught exception: Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/ryu/lib/hub.py", line 52, in _launch
    func(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/ryu/controller/controller.py", line 71, in __call__
    self.server_loop()
  File "/usr/local/lib/python2.7/dist-packages/ryu/controller/controller.py", line 94, in server_loop
    datapath_connection_factory)
  File "/usr/local/lib/python2.7/dist-packages/ryu/lib/hub.py", line 108, in __init__
    self.server = eventlet.listen(listen_info)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/convenience.py", line 43, in listen
    sock.bind(addr)
  File "/usr/lib/python2.7/socket.py", line 224, in meth
    return getattr(self._sock,name)(*args)
error: [Errno 98] Address already in use


解决办法：
kill 掉占用端口号6633的程序
首先查找出是哪个进程占用了该端口号命令为
sudo lsof -i :6633
比如我查出来是
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
ovs-contr 1620 root 4u IPv4 9071 0t0 TCP *:6633 (LISTEN)

显示ovs-contr这个进程占用了6633 那就kill掉这个进程。
kill的时候尽量先切换到root权限 再这参数选-9
kill -9 1620