Android Question Unable to connect to MySQL using jRDC2 on VPS

Setlodi · Feb 6, 2023

Hi there
I hope someone can help me. I have followed Erel's tutorial on configuring B4A and B4J jRDc2 for connecting to a remote MySQL database. This is what I did:

On jRDC B4J
Edited config.properties
DriverClass=com.mysql.jdbc.Driver
JdbcUrl=jdbc:mysql://My-VPS-IP-Address/exampleDB?characterEncoding=utf8
User=root
Password=********

#Java server port
ServerPort=17178

Also:

B4X:

#AdditionalJar: mysql-connector-java-5.1.47-bin

Compiled jRDC and built standalone package

On the VPS:

Installed MySQL
Created exampleDB test database
Created user with root access and granted all privileges
Edited mysqld.cnf to allow all IP's to connect - changed from 127.0.0.1 to 0.0.0.0
Opened ports 3306 and 17178 on the firewall
Confirmed that both 3306 and 17178 ports are listening
Copied compiled jRDC file to VPS in the folder where my exampleDB is located
Ran nohup /usr/lib/jvm/java-11-openjdk-amd64/bin/java -jar /var/lib/mysql/jrdc.jar & > nohup.out & successfully

On B4A

B4X:

Private const rdcLink As String = "http://160.119.254.12:17178/rdc"

The problem is when I run http://160.119.254.12:17178/test, I get the following error:

RemoteServer is running (02/06/2023 08:36:18)
Error fetching connection.

Please help!!

OliverA · Feb 6, 2023

1) If jRDC2 is running on the same server as your MySQL install, DO NOT open up MySQL to the public. That's is one of the main features of jRDC2 - not exposing the DB server to the public.

2) For testing purposes, don't run jRDC2 with nohup. This way you get visual feedback as to what jRDC2 is complaining about. Otherwise, look at the nohup.out file and see what jRDC2 is complaining about. You may need to stop jRDC2 in order for the stout/stderr to be completely flushed to nohup.out

josejad · Feb 6, 2023

Hi:

Setlodi said:
JdbcUrl=jdbc:mysql://My-VPS-IP-Address/exampleDB?characterEncoding=utf8

You're running the jRDC2 server (.jar file) to your server, so, mysql and the jRDC2 are running on the same machine. You should change My-VPS-IP-Adress to localhost, and CLOSE the 3306 port¡¡¡¡

In your B4A app, is where you should use your VPS address to connect to the B4J server through 17178 port.

You should too create a non-root user and assign it just permissions on your database for security reasons. (but this is not a problem for your tests)

By the way, running http://160.119.254.12:17178/test I get

RemoteServer is running (02/06/2023 12:44:52)
Connection successful.

Setlodi · Feb 6, 2023

José J. Aguilar said:
Hi:

You're running the jRDC2 server (.jar file) to your server, so, mysql and the jRDC2 are running on the same machine. You should change My-VPS-IP-Adress to localhost, and CLOSE the 3306 port¡¡¡¡

In your B4A app, is where you should use your VPS address to connect to the B4J server through 17178 port.

You should too create a non-root user and assign it just permissions on your database for security reasons. (but this is not a problem for your tests)

By the way, running http://160.119.254.12:17178/test I get

RemoteServer is running (02/06/2023 12:44:52)
Connection successful.

Hi Jose

Yes I managed to get it working while waiting for the help. I understand what you and OliverA are saying about no opening MySQL to exernal users as the jRDC server is hosted locally in the same server. I will close it.

Setlodi · Feb 6, 2023

Now that the connection is working, I'm now getting an HTTP ERROR 500.

In B4A jRDC mocule:

Private const rdcLink As String = "http://160.119.254.12:17178/rdc"

See the logs below:

Logger connected to: HUAWEI EML-L09
--------- beginning of system
--------- beginning of main
*** Service (starter) Create ***
** Service (starter) Start **
** Activity (main) Create (first time) **
*** mainpage: B4XPage_Created
*** mainpage: B4XPage_Appear
** Activity (main) Resume **
*** Service (httputils2service) Create ***
** Service (httputils2service) Start **
ResponseError. Reason: Server Error, Response: <html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=ISO-8859-1"/>
<title>Error 500 java.sql.SQLException: Parameter index out of range (1 > number of parameters, which is 0).</title>
</head>
<body><h2>HTTP ERROR 500 java.sql.SQLException: Parameter index out of range (1 > number of parameters, which is 0).</h2>
<table>
<tr><th>URI:</th><td>/rdc</td></tr>
<tr><th>STATUS:</th><td>500</td></tr>
<tr><th>MESSAGE:</th><td>java.sql.SQLException: Parameter index out of range (1 > number of parameters, which is 0).</td></tr>
<tr><th>SERVLET:</th><td>anywheresoftware.b4j.object.JServlet-40a4337a</td></tr>
</table>
<hr/><a href="https://eclipse.org/jetty">Powered by Jetty:// 11.0.9</a><hr/>
</body>
</html>
ERROR: <html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=ISO-8859-1"/>
<title>Error 500 java.sql.SQLException: Parameter index out of range (1 > number of parameters, which is 0).</title>
</head>
<body><h2>HTTP ERROR 500 java.sql.SQLException: Parameter index out of range (1 > number of parameters, which is 0).</h2>
<table>
<tr><th>URI:</th><td>/rdc</td></tr>
<tr><th>STATUS:</th><td>500</td></tr>
<tr><th>MESSAGE:</th><td>java.sql.SQLException: Parameter index out of range (1 > number of parameters, which is 0).</td></tr>
<tr><th>SERVLET:</th><td>anywheresoftware.b4j.object.JServlet-40a4337a</td></tr>
</table>
<hr/><a href="https://eclipse.org/jetty">Powered by Jetty:// 11.0.9</a><hr/>
</body>
</html>
** Activity (main) Pause event (activity is not paused). **
*** mainpage: B4XPage_Disappear [mainpage]

OliverA · Feb 7, 2023

The SQL command you have set up in the config.properties file does not contain a parameter (a ?), yet you are passing on a parameter to the query.

Note: Unless you have a modified version of jRDC2, any changes to the config.properties file should be followed by recreating the .jar file and re-uploading/publishing it to the server.

Android Question Unable to connect to MySQL using jRDC2 on VPS

Setlodi

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OliverA

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josejad

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Setlodi

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Setlodi

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OliverA

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