MySQL - Can not connect to the database

Error message:

ERROR 2003 (HY000): Can't connect to MySQL server on '....' (111).

Solution:

1. Check connection details:
1. Verify that the IP is correct.
2. Verify that the Port number is correct.
3. Check username and password.
2. Network issues:
1. Check that connection to VPN or any other connection types.
2. Check Firewall definition.
3. For cloud instances: check that your IP is allowed.
3. Check that MySQL is up:
1. Check that the MySQL service is up:
1. Windows: in the services.
2. Linux: sudo systemctl start <SERVICENAME>
4. MySQL configurations:
1. Max connections - see here: http://copypastenet.blogspot.com/2021/02/mysql-see-orand-change-how-many.html 
2. cnf file configurations.

SAP (sybase) RS - rs_init - Could not connect to ID Server Unable to execute query create connection

The case:

Error when adding a new connection using rs_init: 

Could not connect to ID Server Unable to execute query create connection.

Error message:

WARNING: "Could not connect to ID Server 'ID_RS_NAME'."

Press <return> to continue.

SQL Server message: msg 45, level 12, state 0

WARNING: "Could not connect to ID Server 'ID_RS_NAME'."

Press <return> to continue.

Unable to execute query 'create connection to "ASENAME"."DBNAME" s

et error class rs_sqlserver_error_class set function string class rs_sqlserver_

function_class set username "DBNAME_maint" set password *** with log tr

ansfer on' against server 'RS_NAME'.

Press <return> to continue.

Solution:

The ID Server RS is not available:

1. The RS service is down - start it.
2. Network or connections problems.
3. Any other reason

SAP (sybase) RS - Displays connection data for the Replication Server

In order to displays connection data for the Replication Server, 

connect SRS, and run:

admin show_connections

go

SQL Server: Connect using a different port

Connect using a different port using a comma between the server name/IP and the port:

servername,port 

or 

serverIP,port

netstat - network statistics

netstat is a command displays statistics on all network activities.

main options:

-a Displays all active ports

-n Numerical display of addresses and port numbers

-o Displays the process identifiers (PID)

| grep 11753 - displays information only for IP 11753 (or other filter)

netstat -a -n | grep 11753

Test Open Ports with Telnet

Open cmd and run:
telnet <IP_ADDRESS> <PORT_NUMBER>

Example:
telnet 30.125.40.120 5000

* If telnet doesn't work, turn "Telnet Client" on via "Programs and Features"-->"Installed updates"-->"Turn Windows features on or off".