Port Numbers
=====================


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        **What are UDP Port Numbers?**

        UDP port numbers identify specific applications or services on a host. Each port allows communication with a particular process or service.

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        **Why are UDP Port Numbers useful?**

        They allow the operating system to route incoming UDP packets to the correct application, enabling multiple services to run simultaneously without interference.

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        **How do UDP Port Numbers work?**

        UDP uses **source** and **destination** port numbers (16-bit each) in its header to send packets to the correct application. Ports range from 0 to 65535.

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        **Where are UDP Port Numbers used?**

        Common UDP-based services use well-known ports:

        - **53** – DNS
        - **67/68** – DHCP
        - **123** – NTP
        - **161/162** – SNMP
        - **500** – IPsec

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        **Which OSI layer do UDP Port Numbers belong to?**

        UDP port numbers are part of the **Transport Layer (Layer 4)**, where data is directed to the correct application process.

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        **Are UDP Port Numbers Windows specific?**

        No, port numbers are part of the standard networking stack and are used on all operating systems including Windows, Linux, and macOS.

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        **Are UDP Port Numbers Linux specific?**

        No, UDP port numbers are universally used in all OS environments. Linux assigns and manages them just like other OSes.

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        **Which transport protocol uses Port Numbers in this way?**

        Both **UDP** and **TCP** use port numbers, but UDP does so without the overhead of connections or reliability mechanisms.

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        **Are UDP Port Numbers used in client-server models?**

        Yes. In a typical model, the **server listens** on a fixed port, and the **client uses an ephemeral port** to initiate the request.

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        Topics in this section,

                * :ref:`Learnings in this section <Port_Num_step1>`

                * :ref:`Terminology <Port_Num_step2>`

                * :ref:`Version Info <Port_Num_step3>`

                * :ref:`Port Numbers Basic Setup on Ubuntu using IPv4 <Port_Num_step18>`

                * :ref:`UDP Feature : Port Numbers <Port_Num_step4>`
                
                * :ref:`Reference links <Port_Num_step17>`

.. _Port_Num_step1:

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    .. tab-item:: Learnings in this section

        * In this section, you are going to learn

.. _Port_Num_step2:

.. tab-set::

    .. tab-item:: Terminology
        
       * Terminology


.. _Port_Num_step3:

.. tab-set::

    .. tab-item:: Version Info
    
         * Version Info


.. _Port_Num_step18:

.. tab-set::

   .. tab-item:: Port Numbers Basic Setup on Ubuntu using IPv4
       
      * setup

.. _Port_Num_step4:

.. tab-set::

    .. tab-item:: UDP Feature : Port Numbers

        **Port Numbers - Testcases**

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                :file: ./UDP_Feature9_Port_Numbers_Test_Cases.csv
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.. _Port_Num_step17:

.. tab-set::

    .. tab-item:: Reference links
     
       * Reference links