The classic "Unable to connect to MySQL server" error while the service shows as running can be particularly frustrating. Here's how I typically approach this issue:

# Basic status check
sudo systemctl status mysql
# or
sudo service mysql status

Just because the service is running doesn't guarantee it's accepting connections. Let's test connectivity:

# Command line connection test
mysqladmin -u root -p ping
# Expected output: mysqld is alive

Based on my experience, these are the most likely causes:

# Check if MySQL is listening on expected port
netstat -tlnp | grep mysql
# Typical output should show either:
# tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN
# or
# tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN

Permission problems often masquerade as connection failures:

# Check user privileges
mysql -u root -p -e "SELECT Host,User FROM mysql.user;"

Let's examine the critical configuration parameters:

# Check bind-address in my.cnf
grep -E 'bind-address|skip-networking' /etc/mysql/my.cnf
# For newer installations, check:
grep -E 'bind-address|skip-networking' /etc/mysql/mysql.conf.d/mysqld.cnf

Since you're using Webuzo, these additional checks might help:

# Verify Webuzo's MySQL port configuration
cat /usr/local/Webuzo/etc/config.inc.php | grep MYSQL_PORT
# Check alternative configuration locations
ls -la /usr/local/Webuzo/etc/my*

Don't overlook basic network barriers:

# Check iptables rules
sudo iptables -L -n
# Test local connection
telnet 127.0.0.1 3306

Try connecting with different parameters to isolate the issue:

# Force TCP connection
mysql --protocol=TCP -u username -p
# Or specify host explicitly
mysql -h 127.0.0.1 -u username -p

MySQL error logs often hold the golden ticket:

# Find log location
mysql -u root -p -e "SHOW VARIABLES LIKE 'log_error';"
# Then examine the log
sudo tail -50 /var/log/mysql/error.log

---

When your MySQL server shows as running in terminal (systemctl status mysql) but applications fail to connect, you're dealing with a classic connectivity configuration issue. The "Unable to connect to MySQL server" error typically indicates network accessibility problems rather than service availability.

First, confirm MySQL is actually listening for connections:

sudo netstat -tulnp | grep mysql
# Expected output showing listening ports (usually 3306):
# tcp        0      0 127.0.0.1:3306          0.0.0.0:*               LISTEN      1234/mysqld

If you see 127.0.0.1 instead of 0.0.0.0, MySQL is only accepting local connections.

Edit /etc/mysql/my.cnf or appropriate config file (location varies by OS/distro):

[mysqld]
bind-address = 0.0.0.0
skip-networking = OFF
skip-name-resolve = ON  # Recommended for performance

After changes, restart MySQL:

sudo systemctl restart mysql

Connect locally and check user permissions:

mysql -u root -p
SELECT Host, User FROM mysql.user;
# Ensure your application user has correct host access:
GRANT ALL PRIVILEGES ON *.* TO 'webuzo_user'@'%' IDENTIFIED BY 'password';
FLUSH PRIVILEGES;

Check firewall rules (example for UFW):

sudo ufw allow 3306/tcp
sudo ufw reload

For SELinux (if enabled):

sudo setsebool -P mysqld_connect_any 1

Verify remote connectivity using basic tools:

telnet your_server_ip 3306
# Or for more detailed check:
mysqladmin -h your_server_ip -u username -p ping

Webuzo sometimes uses non-standard socket locations. Check its configuration:

cat /usr/local/webuzo/config/mysql.json
# Ensure socket path matches actual MySQL socket:
ls -l /var/run/mysqld/mysqld.sock

When all else fails, use tcpdump to analyze connection attempts:

sudo tcpdump -i any port 3306 -nn -v
# Look for SYN packets without ACK responses indicating blocked connections