How to find wireless network frequency

There are situations where we need to find out our wireless network frequency.
Eg:- before purchasing network devices we need to verify whether we are in a 2.4 or 5 GHz network

Usage of iwlist command on a linux box,

iwlist <WIRELESS INTERFACE> scanning | grep -C3 <WIRELES_NETWORK_NAME>

Eg:

 iwlist wlp4s0 scanning | grep -C3 VM6292804
                    Frequency:2.412 GHz (Channel 1)
                    Quality=47/70  Signal level=-63 dBm 
                    Encryption key:on
                    ESSID:"VM6292804"
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
                              9 Mb/s; 12 Mb/s; 18 Mb/s
                    Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s

Running different MySQL Servers inside a single host

There are many circumstances where running different MySQL server versions required. Eg:- testing

Spinning MySQL docker instance is the easiest way I have found among multiple methods.

sudo docker run --name mysql56 -p 127.0.0.1:3316:3306 -e MYSQL_ROOT_PASSWORD=root -d mysql:5.6

This command will download and spin a MySQL 5.6 container. At the same time it will map the default 3306 port in to the 3316 of the host machine.

How to hide your application name using nginx proxy_pass directive

For the showcase purpose I will be using the store application which resides inside WSO2 API Manager 2.1.0

Following are API Manager specific configs which needs to be done.

1. Set proxyPort attribute for connector configs resides in <AM_HOME>/repository/conf/tomcat/catalina-server.xml file.

        <Connector protocol="org.apache.coyote.http11.Http11NioProtocol"
                   port="9763"
                   redirectPort="9443"
                   proxyPort="80"
                   bindOnInit="false"
                   maxHttpHeaderSize="8192"
         />

        <Connector protocol="org.apache.coyote.http11.Http11NioProtocol"
                   port="9443"
                   proxyPort="443"
                   bindOnInit="false"
                   sslProtocol="TLS"
                   maxHttpHeaderSize="8192"
          />

Note that I have removed some attributes for brevity.

2. Update reverseProxy configuration resides inside <AM_HOME>/repository/deployment/server/jaggeryapps/store/site/conf/site.json

    "reverseProxy" : {
        "enabled" : true, 
        "host" : "localhost",
        "context":"",
    }

After above changes start/restart the AM node.


Now the Nginx configuration,

Make sure to generate and store SSL certificate and the key within /etc/nginx/ssl directory.

For the explanation purpose I will be having two server blocks, which can be consolidated to a one.

server{
    listen 80;
    server_name localhost;
    location / {
            proxy_pass http://localhost:9763/store/;
            proxy_redirect off;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP      $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            include /etc/nginx/proxy_params;
            proxy_cookie_path ~*^/.* /;
    }
}
server{
    listen 443 ssl;
    ssl_certificate /etc/nginx/ssl/nginx.crt;
    ssl_certificate_key /etc/nginx/ssl/nginx.key;
    server_name localhost;
    location / {
            proxy_pass https://localhost:9443/store/;
            proxy_redirect off;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP      $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            include /etc/nginx/proxy_params;
            proxy_cookie_path ~*^/.* /;
    }
}

After reloading the newly added config browse https://localhost or https://localhost,

Download a part of YouTube video as mp3

I will be using ffmpeg and youtube-dl installed linux distro (Ubuntu 16.04 LTS)

ffmpeg -ss 00:00:00.0000 -i $(youtube-dl -f 22 --get-url <YOUTUBE_LINK>) -t 00:00:00.0000 -acodec libmp3lame -qscale:a 0 sample.mp3

Fill <YOUTUBE_LINK> with the link to YouTube video.

Find further explanation of above command here,

• -ss : start of the stream 00:00:00.0000 stands for hour:minute:second.millisecond
• -i   : provide the input, here we will be using an output from youtube-dl.
• -t   : length of the stream

Further information about bitrate selection (-qscale:a 0) can be found here.

• libmp3lame is the audio encoding used for this purpose.
• sample.mp3 is the output file of above command.

Troubleshooting Firebird Database

Note:  I will be using the employee database(/opt/firebird/examples/empbuild/employee.fdb) which is available by-default with the Firebird 2.5.7  in this post.

How to connect to a Firebird Database and test (using command-line)

1. Go to /opt/firebird/bin directory.
2. Run ./isql (Command-line tool for Firebird)

udara@Razorx1:/opt/firebird/bin$ ./isql
Use CONNECT or CREATE DATABASE to specify a database
SQL>

3. Run connect "/opt/firebird/examples/empbuild/employee.fdb"

SQL> connect "/opt/firebird/examples/empbuild/employee.fdb"
CON>

4. Provide the user/password to connect, note the semicolon (;) at the end.

CON> user 'SYSDBA' password 'admin';
Database:  "/opt/firebird/examples/empbuild/employee.fdb", User: SYSDBA
SQL>

5. Run the intended query,

SQL> select * from employee;

 EMP_NO FIRST_NAME      LAST_NAME            PHONE_EXT                 HIRE_DATE DEPT_NO JOB_CODE JOB_GRADE JOB_COUNTRY                    SALARY FULL_NAME                            
======= =============== ==================== ========= ========================= ======= ======== ========= =============== ===================== =====================================
      2 Robert          Nelson               250       1988-12-28 00:00:00.0000  600     VP               2 USA                         105900.00 Nelson, Robert                       
      4 Bruce           Young                233       1988-12-28 00:00:00.0000  621     Eng              2 USA                          97500.00 Young, Bruce                         
      5 Kim             Lambert              22        1989-02-06 00:00:00.0000  130     Eng              2 USA                         102750.00 Lambert, Kim                         
      8 Leslie          Johnson              410       1989-04-05 00:00:00.0000  180     Mktg             3 USA                          64635.00 Johnson, Leslie                      
      9 Phil            Forest               229       1989-04-17 00:00:00.0000  622     Mngr             3 USA                          75060.00 Forest, Phil                         
     11 K. J.           Weston               34        1990-01-17 00:00:00.0000  130     SRep             4 USA                          86292.94 Weston, K. J.                        
     12 Terri           Lee                  256       1990-05-01 00:00:00.0000  000     Admin            4 USA                          53793.00 Lee, Terri   

How to enable trace configuration

1. Open /opt/firebird/fbtrace.conf in your favorite text editor and update relevant configuration.

How to trace the database

1. Go to /opt/firebird/bin directory.
2. Run ./fbtracemgr with proper parameter set.

udara@Razorx1:/opt/firebird/bin$ ./fbtracemgr -SE service_mgr -START -NAME fire -CONFIG ../fbtrace.conf -USER SYSDBA -PASS admin

Sample trace output for the select * from employee;query.

2017-02-22T11:58:23.2200 (1980:0x7f85df7ae678) TRACE_INIT
    SESSION_4 fire
   

2017-02-22T11:58:23.2210 (1980:0x7f85df7ae678) PREPARE_STATEMENT
    /opt/firebird/examples/empbuild/employee.fdb (ATT_63, SYSDBA:NONE, NONE, TCPv4:127.0.0.1)
    /opt/firebird/bin/isql:7445
        (TRA_264, READ_COMMITTED | NO_REC_VERSION | WAIT | READ_WRITE)

Statement 128:
-------------------------------------------------------------------------------
select * from employee
      0 ms

2017-02-22T11:58:23.2210 (1980:0x7f85df7ae678) FREE_STATEMENT
    /opt/firebird/examples/empbuild/employee.fdb (ATT_63, SYSDBA:NONE, NONE, TCPv4:127.0.0.1)
    /opt/firebird/bin/isql:7445

Statement 127:
-------------------------------------------------------------------------------
select * from employee

2017-02-22T11:58:23.2220 (1980:0x7f85df7ae678) EXECUTE_STATEMENT_START
    /opt/firebird/examples/empbuild/employee.fdb (ATT_63, SYSDBA:NONE, NONE, TCPv4:127.0.0.1)
    /opt/firebird/bin/isql:7445
        (TRA_263, CONCURRENCY | WAIT | READ_WRITE)

Statement 128:
-------------------------------------------------------------------------------
select * from employee

2017-02-22T11:58:23.2260 (1980:0x7f85df7ae678) CLOSE_CURSOR
    /opt/firebird/examples/empbuild/employee.fdb (ATT_63, SYSDBA:NONE, NONE, TCPv4:127.0.0.1)
    /opt/firebird/bin/isql:7445

Statement 128:
-------------------------------------------------------------------------------
select * from employee

Firebird trace utility

Firebird Trace utility.
Usage: fbtracemgr <action> [<parameters>]

Actions:
  -STA[RT]                              Start trace session
  -STO[P]                               Stop trace session
  -SU[SPEND]                            Suspend trace session
  -R[ESUME]                             Resume trace session
  -L[IST]                               List existing trace sessions

Action parameters:
  -N[AME]    <string>                   Session name
  -I[D]      <number>                   Session ID
  -C[ONFIG]  <string>                   Trace configuration file name

Connection parameters:
  -SE[RVICE]  <string>                  Service name
  -U[SER]     <string>                  User name
  -P[ASSWORD] <string>                  Password
  -FE[TCH]    <string>                  Fetch password from file
  -T[RUSTED]  <string>                  Force trusted authentication

Examples:
  fbtracemgr -SE remote_host:service_mgr -USER SYSDBA -PASS masterkey -LIST
  fbtracemgr -SE service_mgr -START -NAME my_trace -CONFIG my_cfg.txt
  fbtracemgr -SE service_mgr -SUSPEND -ID 2
  fbtracemgr -SE service_mgr -RESUME -ID 2
  fbtracemgr -SE service_mgr -STOP -ID 4

Firebird sample with WSO2 DSS

I'm going to provide instructions to showcase how we can use Firebird data-source with WSO2 DSS.

Note:
I will be using the employee database(/opt/firebird/examples/empbuild/employee.fdb) which is available by-default with the Firebird 2.5.7  in this post.

Following are the Firebird/JDBC driver and WSO2 DSS versions which I have tried.

• Firebird: 2.5.X
• JDBC Driver: jaybird-full-2.2.12
• WSO2 DSS: 3.5.1

Steps:

1. Download the JDBC driver for Firebird and copy into the <DSS_HOME>/repository/components/lib/ directory.
2. Start the DSS node.(or restart if it's already started)
3. Add a new Data Service with the following configuration.

Datasource type: RDBMS

Database Engine: Generic

Driver Class: org.firebirdsql.jdbc.FBDriver

URL: jdbc:firebirdsql://localhost:3050//opt/firebird/examples/empbuild/employee.fdb

* Provide Host, Port, Database Path, User Name, Password accordingly.

Create and test the Datasource connection.

Save and proceed next, to add the query

select EMP_NO,FIRST_NAME,
LAST_NAME,PHONE_EXT,HIRE_DATE,DEPT_NO,SALARY from employee where EMP_NO=:EMP_NO

Add Input/Output mappings accordingly.

Save and proceed next, to add the operation.

 

Save and finish.

Now if you go to the Home> Manage> Services> List> firebirdTest> Edit Data Source(XML Edit) you can see the following Data Service definition.

<data disableStreaming="true" name="firebirdTest" transports="http https local">
   <config enableOData="false" id="emp">
      <property name="driverClassName">org.firebirdsql.jdbc.FBDriver</property>
      <property name="url">jdbc:firebirdsql://localhost:3050//opt/firebird/examples/empbuild/employee.fdb</property>
      <property name="username">SYSDBA</property>
      <property name="password">admin</property>
   </config>
   <query id="select" useConfig="emp">
      <sql>select EMP_NO,FIRST_NAME,&#xd;LAST_NAME,PHONE_EXT,HIRE_DATE,DEPT_NO,SALARY from employee where EMP_NO=:EMP_NO</sql>
      <result element="Entries" rowName="Entry">
         <element column="EMP_NO" name="EMP_NO" xsdType="string"/>
         <element column="FIRST_NAME" name="FIRST_NAME" xsdType="string"/>
         <element column="LAST_NAME" name="LAST_NAME" xsdType="string"/>
         <element column="PHONE_EXT" name="PHONE_EXT" xsdType="string"/>
         <element column="HIRE_DATE" name="HIRE_DATE" xsdType="string"/>
         <element column="DEPT_NO" name="DEPT_NO" xsdType="string"/>
         <element column="SALARY" name="SALARY" xsdType="string"/>
      </result>
      <param name="EMP_NO" sqlType="STRING"/>
   </query>
   <operation disableStreaming="true" name="getEmp">
      <call-query href="select">
         <with-param name="EMP_NO" query-param="EMP_NO"/>
      </call-query>
   </operation>
</data>

How to test the data-service(Try-it tool)

Go to Home> Manage> Services> List> firebirdTest> Try this service.

Provide the EMP_NO and press send.

Further information on query/input and output mappings/operation can be found here.