Use Flask error

First, follow written a very simple application Flask, direct error

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "1234"
if __name__=="__main__":
    app.run()

Report an error

Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "D:\python\install\helpers\pydev\_pydev_bundle\pydev_umd.py", line 197, in runfile
    pydev_imports.execfile(filename, global_vars, local_vars)  # execute the script
  File "D:\python\install\helpers\pydev\_pydev_imps\_pydev_execfile.py", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc)
  File "E:/Python/UseTest.py", line 8, in <module>
    app.run()
  File "C:\Users\youziku\AppData\Roaming\Python\Python36\site-packages\flask\app.py", line 990, in run
    run_simple(host, port, self, **options)
  File "C:\Users\youziku\AppData\Roaming\Python\Python36\site-packages\werkzeug\serving.py", line 1009, in run_simple
    inner()
  File "C:\Users\youziku\AppData\Roaming\Python\Python36\site-packages\werkzeug\serving.py", line 962, in inner
    fd=fd,
  File "C:\Users\youziku\AppData\Roaming\Python\Python36\site-packages\werkzeug\serving.py", line 805, in make_server
    host, port, app, request_handler, passthrough_errors, ssl_context, fd=fd
  File "C:\Users\youziku\AppData\Roaming\Python\Python36\site-packages\werkzeug\serving.py", line 698, in __init__
    HTTPServer.__init__(self, server_address, handler)
  File "C:\Program Files (x86)\Microsoft Visual Studio\Shared\Python36_64\lib\socketserver.py", line 453, in __init__
    self.server_bind()
  File "C:\Program Files (x86)\Microsoft Visual Studio\Shared\Python36_64\lib\http\server.py", line 138, in server_bind
    self.server_name = socket.getfqdn(host)
  File "C:\Program Files (x86)\Microsoft Visual Studio\Shared\Python36_64\lib\socket.py", line 673, in getfqdn
    hostname, aliases, ipaddrs = gethostbyaddr(name)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xb3 in position 8: invalid start byte

I stepped on the mine for two days, and now record what, error-prone points

1) is a coding problem code, will re-save the page to utf-8.

2) computer name is Chinese, and the user name is Chinese

3) port is used to manually specify the port

When the current two useless, you may wish to specify what port

if __name__ == '__main__':
    app.run(host="0.0.0.0", debug=True, port=9999)