📋

Description

This error indicates that the MySQL client application was unable to establish a network connection with the MySQL server. It typically occurs when the client cannot reach the specified host and port, preventing any database operations from succeeding.

💬

Error Message

Can't connect to MySQL server on '%s:%u' (%d)

🔍

Known Causes

4 known causes

⚠️

MySQL Server Offline

The MySQL server process is not actively running on the specified host, preventing any incoming connections.

⚠️

Wrong Connection Details

The client application is attempting to connect to an incorrect hostname, IP address, or port number where the MySQL server is not listening.

⚠️

Firewall Blockage

A firewall on either the client or server machine is blocking the network traffic on the MySQL port (default 3306).

⚠️

Network Connectivity Issues

General network problems, such as DNS resolution failures or routing issues, are preventing communication between the client and server.

🛠️

Solutions

5 solutions available

1. Check MySQL Server is Running easy

Ensure the server is started and listening

1

Check MySQL status

# Linux
sudo systemctl status mysql

# macOS
brew services list | grep mysql

# Windows
net start | findstr MySQL

2

Start MySQL if stopped

# Linux
sudo systemctl start mysql

# macOS  
brew services start mysql

# Windows
net start MySQL80

2. Check Host and Port easy

Verify correct hostname and port number

1

Verify MySQL is listening

# Check if MySQL is listening on expected port
netstat -tlnp | grep 3306
# or
ss -tlnp | grep 3306

2

Test connection with correct port

mysql -u user -p -h hostname -P 3306

3

Check bind-address in my.cnf

[mysqld]
# 0.0.0.0 allows remote connections
bind-address = 0.0.0.0
# 127.0.0.1 only allows local connections
# bind-address = 127.0.0.1

3. Check Firewall Rules medium

Allow MySQL port through firewall

1

Linux (iptables/ufw)

# UFW
sudo ufw allow 3306/tcp

# iptables
sudo iptables -A INPUT -p tcp --dport 3306 -j ACCEPT

2

Windows Firewall

netsh advfirewall firewall add rule name="MySQL" dir=in action=allow protocol=tcp localport=3306

3

Check cloud provider security group

# AWS/GCP/Azure - add inbound rule:
# Protocol: TCP
# Port: 3306
# Source: Your IP or range

4. Fix Network Connectivity medium

Troubleshoot network issues

1

Test basic connectivity

# Ping the host
ping mysql-server-host

# Test port with telnet
telnet mysql-server-host 3306

# Or with nc
nc -zv mysql-server-host 3306

2

Check DNS resolution

nslookup mysql-server-host
# or
dig mysql-server-host

3

Try IP address instead of hostname

mysql -u user -p -h 192.168.1.100 -P 3306

5. Check skip-networking Setting medium

Ensure MySQL allows TCP connections

1

Check if skip-networking is enabled

# In MySQL (if you can connect locally):
SHOW VARIABLES LIKE 'skip_networking';

2

Disable skip-networking in my.cnf

[mysqld]
# Remove or comment out:
# skip-networking

# Make sure this is NOT set:
# skip-networking = 1

3

Restart MySQL

sudo systemctl restart mysql

🔗

Related Errors

5 related errors

MySQL Error 2003: Server Connection Failure