Develop Reference

PyMySQL using localhost vs socket incoherant behaviour

I am using PyMySQL to connect to a database running on localhost. I can access the database just fine using the username/password combiunation in both the command line and adminer so the database does not appear to be the probem here.
My code is as follow. However, when using the host="127.0.0.1" options, I get an OperationalError and an Errno 111. Using the same code, but connecting via the socket Mariadb runs on is fine.
import pymysql.cursors
from pprint import pprint
# This causes an OperationalError: (pymysql.err.OperationalError) (2003, "Can't connect to MySQL server on 'localhost' ([Errno 111] Connection refused)")
# connection = pymysql.connect(
# host="127.0.0.1",
# port=3306,
# user="root",
# password="S3kr37",
# db="my_test",
# )
# This works.
connection = pymysql.connect(
user="root",
password="S3kr37",
db="my_test",
unix_socket="/var/lib/mysql/mysql.sock"
)
try:
with connection.cursor() as cursor:
sql = "select * from MySuperTable"
cursor.execute(sql)
results = cursor.fetchall()
pprint(results)
finally:
connection.close()
What am I doing wrong?
PS: Note that this question has the same problem but the solution offered is the socket. That is no good enough: I want to know why I cannot use the hostname as the documentation suggests.

Errorcode 2003 (CR_CONN_HOST_ERROR) is returned by the client library, in case the client wasn't able to establish a tcp connection to the server.
First you should check, if you can connect via telnet or mysql command line client to your server.
If not, check the server configuration file:
does the server run on port 3306?
is IPv4 disabled?
is skip-networking enabled?
is bind-address activated (with another IP?

SSL connection error: SSL certificate validation failure (2026) (SQLDriverConnect) pyodbc?

I am trying to connect to Azure MySQL Database Service. I am using
pyodbc==3.0.3
python 2.7
My Connection string looks like this
connection_string = "DRIVER={MySQL};SERVER={server_name}.mysql.database.azure.com;PORT=3306;DATABASE" \
"={my_database_name};UID={username#server_name};PWD={password};CHARSET=UTF8;" \
"sslca=/home/sachin/BaltimoreCyberTrustRoot.crt.pem;sslverify=1"
cnxn = pyodbc.connect(connection_string)
But the same configuration works with mymysql.connector is working fine.
import mysql.connector
cnx = mysql.connector.connect(user="{username#servername}", password="{password}",
host="{server_name}.mysql.database.azure.com",
port=3306, database="{database_name}", ssl_ca="/home/sachin//root.crt",
ssl_verify_cert=True)
cnx.cursor()
I can not use mysql.connector for now. So need some suggestion if any one have faced this issue.

I had the same problem and fixed it by setting sslverify=1 to sslverify=0.
e.g. for Azure:
;sslca={BaltimoreCyberTrustRoot.crt.pem}; sslverify=0; Option=3;'

Connection to external MySQL instance using Python

I have tried the following code:
MySQLdb.connect(host='xxx', port=3306, user='yyy')
But I get the following error:
(2005, "Unknown MySQL server host ...
I have tried to remove all firewall restrictions on the external MySQL instance, as a test. I am able to connect to the instance from my developing machine.
I believe this should be possible now that the App Engine supports sockets, or am I wrong?

I think this connection is not allowed (no external socket support in MySQLdb) :
https://developers.google.com/appengine/docs/python/cloud-sql/?hl=en#Python_Using_a_local_MySQL_instance_during_development
You have to use localhost/127.0.0.1 or CloudSQL socket (unix_socket='/cloudsql/'):
if (os.getenv('SERVER_SOFTWARE') and
os.getenv('SERVER_SOFTWARE').startswith('Google App Engine/')):
db = MySQLdb.connect(unix_socket='/cloudsql/' + _INSTANCE_NAME, db='guestbook', user='root')
else:
db = MySQLdb.connect(host='127.0.0.1', port=3306, user='root')
# Alternately, connect to a Google Cloud SQL instance using:
# db = MySQLdb.connect(host='ip-address-of-google-cloud-sql-instance', port=3306, user='root')

PyMySQL can't connect to MySQL on localhost

I'm trying to connect to MySQL on localhost using PyMySQL:
import pymysql
conn = pymysql.connect(db='base', user='root', passwd='pwd', host='localhost')
but (both on Python 2.7 and Python 3.2) I get the error:
socket.error: [Errno 111] Connection refused
pymysql.err.OperationalError: (2003, "Can't connect to MySQL server on 'localhost' (111)")
I'm sure mysqld is running because I can connect using mysql command or phpMyAdmin. Moreover, I can connect using MySQLdb on Python 2 with nearly the same code:
import MySQLdb
conn = MySQLdb.connect(db='base', user='root', passwd='pwd', host='localhost')
It seems that the problem is on PyMySQL side rather than MySQL but I have no idea how to solve it.

Two guesses:
Run mysqladmin variables | grep socket to get where the socket is located, and try setting up a connection like so:
pymysql.connect(db='base', user='root', passwd='pwd', unix_socket="/tmp/mysql.sock")
Run mysqladmin variables | grep port and verify that the port is 3306. If not, you can set the port manually like so:
pymysql.connect(db='base', user='root', passwd='pwd', host='localhost', port=XXXX)

Seems like changing localhost to 127.0.0.1 fixes the error, at least in my configuration.
If it doesn't, I would look for errors in tcp sockets connection and, of course, post it as a bug in pymysql bugtrack.

I solved the issue by replacing localhost with 127.0.0.1 and changing the password to my MYSQL database password as shown below;
conn = pymysql.connect(
host = '127.0.0.1',
port = 3306,
user = 'root',
passwd = 'XXXXXXXXX',
db = 'mysql'
)

I met the same question and my solution is as follows:
Run ssh -fN -L 3307:mysql_host:3306 ssh_user#ssh_host in my terminal.
Then input your ssh password
conn = pymysql.connect(db='base', user='root', passwd='pwd', host='localhost')
This error occurs because database does not support link directly.

I asked why socket worked but not TCP and the answer was that bind-address in /etc/my.cnf was not set correctly. This could be your problem too since the socket methods works just fine but the TCP one does not.

Those who are strugging to connect localhost MySQL from dockerised flask-sqlalchemy or using pymysql, pls look into this thread, very usefull How to connect locally hosted MySQL database with the docker container

This worked for me:
import pymysql
db = pymysql.connect(host="localhost",port=8889,user="root",passwd="root")
cursor=db.cursor()
cursor.execute("SHOW DATABASES")
results=cursor.fetchall()
for result in results:
print (result)
if you want to find the port # go to mysql in terminal, and type:
SHOW VARIABLES WHERE Variable_name = 'hostname';
SHOW VARIABLES WHERE Variable_name = 'port';

I had this same problem on AWS - and turns out that my security group was blocking the connection. I temporarily opened up all connections and voila! It connected!
Do you have any type of FW or host-based FW that could be blocking the connection? I thought it was my code and all was fine. Also check the port you are connecting on.

If you are using Docker, you might need to use host.docker.internal instead of localhost.

I managed to solve my issue by using the port without any quotation like so:
port = 3306,

You need to add the port to the connection as well. Try this and it works fine.
pymysql(Module Name).connect(host="localhost", user="root", passwd="root", port=8889, db="db_name")

python mysql connection problem

This code works fine:
import MySQLdb
db = MySQLdb.connect("localhost", "root", "","bullsorbit")
cursor = db.cursor()
cursor.execute("Select * from table where conditions'")
numrows = int(cursor.rowcount)
print 'Total number of Pages : %d ' % numrows
but if I give my IP address
db = MySQLdb.connect("192.168.*.*", "root", "","bullsorbit")
it will give this error
super(Connection, self).__init__(*args, **kwargs2)
_mysql_exceptions.OperationalError: (2003, "Can't connect to MySQL server on 'ip address' (111)")

Code 2003 is a standard MySQL client error:
Error: 2003 (CR_CONN_HOST_ERROR) Message: Can't connect to MySQL server on '%s' (%d)
I'd guess that your user is not allowed to connect to the MySQL server using an iP-address. What happens if you try a connection usign the MySQL commandline client?
$ mysql --host=192.168.1.1 -u root bullsorbit

with localhost you connect via loopback-interface.
with ip-addr you connect - as you connect from extern.
if your server allows only the local (loopback) connection
your ip-addr connection fails. (security!)
look at your mysql config, maybe only local-connections are allowed.
is the skip-networking switch off (in the mysql-conf) ?
#skip-networking

For the 2003 error, another possibility is that too many connections are being attempted in too short of time. I noticed this same behavior when I had 127.0.0.1 as my connect string. First I replaced it with localhost which got me further but still the same 2003 error. Then I saw that if I scaled back the number of calls the error disappeared completely.

Instead of:
db = MySQLdb.connect("192.168..", "root", "","bullsorbit")
try:
db = MySQLdb.connect(user="root", host="192.168..", db="bullsorbit")
Password will default to empty string and try the usual identity methods. Host will also default to localhost on default port.