OperationalError: (OperationalError) (2003, "Can't connect to MySQL server on '192.168.129.139' (111)") None None

Question

I am trying to create a remote database using mysql on an Ubuntu machine running 12.04.

It has a root user with remote login enabled and no password.I have started the server.

output of

sudo netstat -tap | grep mysql

shows

tcp        0      0 localhost:mysql         *:*                     LISTEN      13246/mysqld

I have created a database called nwtopology using (as mentioned root doesn't have a password yet.)

 create database nwtopology
 grant all privileges on *.* to [email protected]
 FLUSH PRIVILEGES;

From the client machine that also runs Ubuntu 12.04 I use a python script to connect to the remote mysql database using sqlalchemy.

from pox.core import core
import pox.openflow.libopenflow_01 as of
import re
import datetime
import time
from sqlalchemy import create_engine, ForeignKey
from sqlalchemy import Column, Date, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship, backref
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.sql.expression import exists

log = core.getLogger()
engine = create_engine('mysql://[email protected]/nwtopology', echo=False)
Base = declarative_base()
Session = sessionmaker(bind=engine)
session = Session()

class SourcetoPort(Base):
    """"""
    __tablename__ = 'source_to_port'
    id = Column(Integer, primary_key=True)
    port_no        = Column(Integer)
    src_address    = Column(String,index=True)

    #-----------------------------------------
    def __init__(self, src_address,port_no):
        """"""
        self.src_address = src_address
        self.port_no     = port_no

The create_engine() call is failing with the following error.

POX 0.1.0 (betta) / Copyright 2011-2013 James McCauley, et al.
Traceback (most recent call last):
  File "/home/karthik/ms_thesis/pox/pox/boot.py", line 89, in do_import2
    __import__(name, globals(), locals())
  File "/home/karthik/ms_thesis/pox/custom/tutorial.py", line 39, in <module>
    Base.metadata.create_all(engine)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/schema.py", line 2515, in create_all
    tables=tables)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 2230, in _run_visitor
    conn = self.contextual_connect(close_with_result=False)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 2340, in contextual_connect
    self.pool.connect(),
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 210, in connect
    return _ConnectionFairy(self).checkout()
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 371, in __init__
    rec = self._connection_record = pool._do_get()
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 697, in _do_get
    con = self._create_connection()
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 174, in _create_connection
    return _ConnectionRecord(self)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 256, in __init__
    self.connection = self.__connect()
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 316, in __connect
    connection = self.__pool._creator()
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/strategies.py", line 80, in connect
    return dialect.connect(*cargs, **cparams)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/default.py", line 280, in connect
    return self.dbapi.connect(*cargs, **cparams)
  File "/usr/lib/python2.7/dist-packages/MySQLdb/__init__.py", line 81, in Connect
    return Connection(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/MySQLdb/connections.py", line 187, in __init__
    super(Connection, self).__init__(*args, **kwargs2)
OperationalError: (OperationalError) (2003, "Can't connect to MySQL server on '192.168.129.139' (111)") None None

I cannot figure out why this is happening?Any help is greatly appreciated?

Solution

Looks like the mysql server is configured to listen only on localhost.

You can test this by running telnet 192.168.129.139 3306 from your client machine.

Most probable reason - mysqld (=MySQL daemon) is configured to do so.

Please try to follow Configuration step described here:

Edit the /etc/mysql/my.cnf file to configure MySQL to listen for connections from network hosts, change the bind-address directive to the server's IP address. For example, in your case, replace 192.168.0.5 with 192.168.129.139.

From:

bind-address            = 192.168.0.5

to:

bind-address            = 192.168.129.139

If there is no such entry and you cannot connect, create a new line. You may also try commenting out the line instead.

After making a change to /etc/mysql/my.cnf the MySQL daemon will need to be restarted:

sudo systemctl restart mysql.service

Then test with telnet or by running your application once again. Also netstat would have second entry for mysqld.

Comments

[Jeel Shah]

+1 Thanks for a clear outline. If someone does this and still cannot connect (and is running Ubuntu) then check your firewall settings and allow 3306 as a port.

[MBR]

I also had to create a new user with sufficient privileges that could connect from the outside (see here).

[Yahya]

I followed what is given in the answer but still could not get it to work. I then figured out that the "bind-address" parameter is in the "/etc/mysql/mysql.conf.d/mysqld.cnf" file. Commented it out over there and it worked!

[Stefan Falk]

Link is dead by now.

[questionto42standswithUkraine]

@StefanFalk Yes, you need to replace the old ubuntu number by a newer one like 18, now edited. In future, that will have to be done again, just search for a newer version if it is dead again.