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I am having a hard time understanding what I'm doing wrong while trying to connect to a database that is hosted on a domain from https://www.biz.nf/. My java web app using tomcat server runs on localhost:8080 while the database is served at fdb27.biz.nf on port 3306. Does the database and server have to be running on the same port? I tried changing the bind address in program data /MySQL/ my.cnf to the ip address of my network and it didn't change anything. Also tried changing the bind-address to 0.0.0.0 and even commenting it out.

I am connecting to the mysql database like this(DBNAME is just a replacement of my actual database name):

Class.forName("com.mysql.cj.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://fdb27.biz.nf:3306/DBNAME", DBNAME, password);

My error log:

    Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:64)
    at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)
    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151)
    at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167)
    at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:89)
    at com.mysql.cj.NativeSession.connect(NativeSession.java:144)
    at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:953)
    at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:823)
    ... 32 more
Caused by: java.net.ConnectException: Connection refused: connect
    at java.base/sun.nio.ch.Net.connect0(Native Method)
    at java.base/sun.nio.ch.Net.connect(Net.java:574)
    at java.base/sun.nio.ch.Net.connect(Net.java:563)
    at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:588)
    at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:333)
    at java.base/java.net.Socket.connect(Socket.java:648)
    at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:155)
    at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:63)
    ... 35 more

EDIT:
Verified IP / URL is correct
JDBC is recognized
DB server is up and running
Ports open for all network interfaces: 3306, 5900, 33060

 Z:\>netstat -ano | find "3306"
  TCP    0.0.0.0:3306           0.0.0.0:0              LISTENING       30152
  TCP    0.0.0.0:33060          0.0.0.0:0              LISTENING       30152
  TCP    127.0.0.1:3306         127.0.0.1:53033        ESTABLISHED     30152
  TCP    127.0.0.1:3306         127.0.0.1:53034        ESTABLISHED     30152
  TCP    127.0.0.1:53033        127.0.0.1:3306         ESTABLISHED     30376
  TCP    127.0.0.1:53034        127.0.0.1:3306         ESTABLISHED     30376
  TCP    [::]:3306              [::]:0                 LISTENING       30152
  TCP    [::]:33060             [::]:0                 LISTENING       30152
begin_to_code11
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  • *"Does the database and server have to be running on the same port?"* no. Looks like a configuration problem. Either on your database or your network. – Federico klez Culloca Mar 10 '21 at 15:31
  • Does this answer your question? [What can be the reasons of connection refused errors?](https://stackoverflow.com/questions/2333400/what-can-be-the-reasons-of-connection-refused-errors) ( "Caused by: java.net.ConnectException: Connection refused: connect" ) – Luuk Mar 10 '21 at 15:32
  • @Luuk Thanks, It turns out that the company did not support outgoing http connections to the database. – begin_to_code11 Mar 15 '21 at 14:30

1 Answers1

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You can check https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_bind_address for version 8.0.13 and newer 0.0.0.0 are not allowed. You can try to put you external IP (you can check it e.g. https://myexternalip.com/), but if you have dynamic IP it will be only temporary solution.

For development purpose consider setup local database or docker with database. Maybe think about getting jdbc url from properties and prepare developer and production properties.

Grzegorz
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