Basic example raw af inet tcp server and client
=================================================

.. tab-set::

    .. tab-item:: IPv4 RAW_AF_INET TCP

        * In this program, you are going to learn
        
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                * How to create a Socket ?

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                * How to bind a socket ?

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                * How to send a data ?

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                * How to recv a data ?  

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                * How to use socket APIs ?

                        * `socket <https://man7.org/linux/man-pages/man2/socket.2.html>`_

                        * `bind <https://man7.org/linux/man-pages/man2/bind.2.html>`_

                        * `sendto <https://man7.org/linux/man-pages/man2/send.2.html>`_

                        * `recvfrom <https://man7.org/linux/man-pages/man2/recv.2.html>`_

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                Topics in this section,

                        * :ref:`program 1: tcp single server and single client : single data transfer <ipv4_raw_af_inet_tcp_single_data_transfer>`  
                        * :ref:`program 2: tcp single server and single client : multiple data transfer <ipv4_raw_af_inet_tcp_multiple_data_transfer>`      
        
.. _ipv4_raw_af_inet_tcp_single_data_transfer:

.. tab-set::

        .. tab-item:: program 1 : tcp single server and single client : single data transfer

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                        Topics in this section,

                                * :ref:`IPV4 RAW_AF_INET TCP SOCKET FAQs <basic_example_ipv4_raw_af_inet_tcp_socket>`
                                * :ref:`Program1 : Step 1: Sequence Diagram for SERVER.c <program1_ipv4_raw_af_inet_tcp_socket_server_sequence_diagram>`
                                * :ref:`Program1 : Step 2: Program for Server.c <program1_ipv4_raw_af_inet_tcp_socket_server_code>`
                                * :ref:`Program1 : Step 3: Compile and Execute Server.c <program1_ipv4_raw_af_inet_tcp_socket_server_side_compile_and_execute>`
                                * :ref:`Program1 : Step 4: Sequence Diagram for CLIENT.c <program1_ipv4_raw_af_inet_tcp_socket_client_sequence_diagram>`
                                * :ref:`Program1 : Step 5: Program for Client.c <program1_ipv4_raw_af_inet_tcp_socket_client_code>`
                                * :ref:`Program1 : Step 6: Compile and Execute Client.c <program1_ipv4_raw_af_inet_tcp_socket_client_side_compile_and_execute>`
                                * :ref:`Summary <basic_example_ipv4_raw_af_inet_tcp_summary>`

.. _ipv4_raw_af_inet_tcp_multiple_data_transfer:

.. tab-set::

        .. tab-item:: program 2 : tcp single server and single client : multiple data transfer

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                        Topics in this section,

                                * :ref:`IPV4 RAW_AF_INET TCP SOCKET FAQs <basic_example_ipv4_raw_af_inet_tcp_socket>`
                                * :ref:`Program2 : Step 1: Sequence Diagram for SERVER.c <program2_ipv4_raw_af_inet_tcp_socket_server_sequence_diagram>`
                                * :ref:`Program2 : Step 2: Program for Server.c <program2_ipv4_raw_af_inet_tcp_socket_server_code>`
                                * :ref:`Program2 : Step 3: Compile and Execute Server.c <program2_ipv4_raw_af_inet_tcp_socket_server_side_compile_and_execute>`
                                * :ref:`Program2 : Step 4: Sequence Diagram for CLIENT.c <program2_ipv4_raw_af_inet_tcp_socket_client_sequence_diagram>`
                                * :ref:`Program2 : Step 5: Program for Client.c <program2_ipv4_raw_af_inet_tcp_socket_client_code>`
                                * :ref:`Program2 : Step 6: Compile and Execute Client.c <program2_ipv4_raw_af_inet_tcp_socket_client_side_compile_and_execute>`
                                * :ref:`Summary <basic_example_ipv4_raw_af_inet_tcp_summary>`

.. _basic_example_ipv4_raw_af_inet_tcp_socket:
        
.. tab-set::

        .. tab-item:: IPV4 RAW_AF_INET TCP SOCKET : FAQs

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                        Let us answer few basic questions in this socket
                
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                        What does ``socket(AF_INET, SOCK_RAW, IPPROTO_TCP)`` do?

                        .. dropdown:: See Answer
                                
				This call creates a raw socket in the ``AF_INET`` address family for direct access to TCP packets.

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			When is it appropriate to use ``SOCK_RAW`` sockets with TCP?

                        .. dropdown:: See Answer
                                
				It's suitable for tasks like packet capturing, network monitoring, or 
				implementing custom protocols where direct access to TCP packets is needed.

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			Can this socket be used for regular TCP communication?

                        .. dropdown:: See Answer
                                
				While technically possible, it's not recommended for regular 
				communication due to increased complexity and potential security risks.

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			How does a raw TCP socket differ from a regular TCP socket?

                        .. dropdown:: See Answer
                                
				A raw TCP socket provides direct access to the TCP layer, allowing for manual packet manipulation, 
				whereas regular TCP sockets handle packet details internally.

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			What are some use cases for raw TCP sockets?

                        .. dropdown:: See Answer
                                
				Use cases include network sniffing, packet analysis, security auditing, and developing custom network protocols.

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			How can I capture and analyze TCP packets using raw sockets?

                        .. dropdown:: See Answer
                                
				You can use the raw socket to capture TCP packets and analyze them using packet analysis tools like Wireshark.

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			Is error checking needed after creating the socket?

                        .. dropdown:: See Answer
                                
				Yes, checking for errors ensures that the socket is created successfully before proceeding with further operations.

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			Why is it important to check the return value of sendto() and recvfrom() in socket programming?

                        .. dropdown:: See Answer
                                
				It detects issues such as network errors or closed connections.

.. _program1_ipv4_raw_af_inet_tcp_socket_server_sequence_diagram:
                
.. tab-set::

    .. tab-item:: Program1 : Step 1: Sequence Diagram for SERVER.c
        
        .. plantuml::
        
           @startuml
	   !theme spacelab
           start
           :socket(AF_INET, SOCK_RAW, IPPROTO_TCP);
           :bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));
           :recvfrom(server_socket, buffer, sizeof(buffer), 0, NULL, NULL);
           :(void)close(server_socket;
           stop
           @enduml

.. _program1_ipv4_raw_af_inet_tcp_socket_server_code:

.. tab-set::

    .. tab-item:: Program1: step 2: program for server.c

        * There are many functions used in socket. We can classify those functions based on functionalities.

                * Create Socket

                * Bind Socket

                * Recvfrom data_packet

                * Sendto data_packet

                * Close socket

        * ``socket()`` is used to create a new socket. For example,

        .. code-block:: c

                server_socket = socket(AF_INET, SOCK_RAW, IPPROTO_TCP);                    

        * ``bind()`` is used to associate the socket with a specific address and port. For example,

        .. code-block:: c
                
                ret = bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));

	* ``recvfrom`` is commonly used with sockets, where communication is connectionless. it provides information about the source (sender) of the data, including the sender's IP address and port number. For example,

        .. code-block:: c

                len  = recvfrom(server_socket, buffer, sizeof(buffer), 0, NULL, NULL);

        * ``close`` is used to close the socket To free up system resources associated with the socket. For example,

        .. code-block:: c

                (void)close(server_socket);

        * See the full program below,

        .. literalinclude:: single_data_transfer/server/server.c
                :language: c
                :emphasize-lines: 72, 73, 74, 86, 87, 88, 98, 99, 109
 
.. _program1_ipv4_raw_af_inet_tcp_socket_server_side_compile_and_execute:

.. tab-set::

    .. tab-item:: Program1 : Step 3: Compile and Execute Server.c
        
        .. code-block:: c
                :emphasize-lines: 1, 3
                
                $ gcc -o server server.c

                $ sudo ./server 127.0.0.1

		IP Address: 127.0.0.1
		Serverlisten
		Receivedpacket:_Hello from client!

.. _program1_ipv4_raw_af_inet_tcp_socket_client_sequence_diagram:

.. tab-set::

    .. tab-item:: Program1 : Step 4: Sequence Diagram for CLIENT.c
        
        .. plantuml::
        
           @startuml
	   !theme spacelab
           start
           :socket(AF_INET, SOCK_RAW, IPPROTO_TCP);
	   :sendto(client_socket, buffer + 3, sizeof(struct iphdr) + sizeof(struct tcphdr) + len, 0, (struct sockaddr*)&server_addr, sizeof(server_addr));
           :(void)close(client_socket);
           stop
           @enduml
  
.. _program1_ipv4_raw_af_inet_tcp_socket_client_code: 

.. tab-set::

    .. tab-item:: Program1 : step 5: program for client.c

        * There are many functions used in socket. We can classify those functions based on functionalities.

                * Create Socket

                * Sendto data_packet

                * Close socket

        * ``socket`` is used to create a new socket. For example,

        .. code-block:: c

               client_socket = socket(AF_INET, SOCK_RAW, IPPROTO_TCP);

        * ``sendto`` is used to send the encoded message to the specified server address and port using a socket. For example,

        .. code-block:: c

		ret = sendto(client_socket, buffer + 3, sizeof(struct iphdr) + sizeof(struct tcphdr) + len, 0, (struct sockaddr*)&server_addr, sizeof(server_addr));

	* ``close`` is used to close the socket To free up system resources associated with the socket. For example,

        .. code-block:: c

                (void)close(client_socket);

        * See the full program below,
        
        .. literalinclude:: single_data_transfer/client/client.c
                :language: c
                :emphasize-lines: 97, 98, 99, 118, 119, 120, 121, 122, 132

.. _program1_ipv4_raw_af_inet_tcp_socket_client_side_compile_and_execute:

.. tab-set::

    .. tab-item:: Program1 : Step 6: Compile and Execute Client.c
        
        .. code-block:: c
                :emphasize-lines: 1, 3

                $ gcc -o client client.c

                $ sudo ./client 127.0.0.1

		IP Address: 127.0.0.1
		Sentpacket:Hello from client!
 
.. _program2_ipv4_raw_af_inet_tcp_socket_server_sequence_diagram:

.. tab-set::

    .. tab-item:: Program2 : Step 1: Sequence Diagram for SERVER.c
        
        .. plantuml::
        
           @startuml
	   !theme spacelab
           start
           :socket(AF_INET, SOCK_RAW, IPPROTO_TCP);
           :bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));
           :i = 0;
           while (while (i < NUM_MESSAGES)) is (yes)
           :recvfrom(server_socket, buffer, sizeof(buffer), 0, NULL, NULL);
           :++i;
           endwhile
           :(void)close(server_socket);
           stop
           @enduml
        
.. _program2_ipv4_raw_af_inet_tcp_socket_server_code:

.. tab-set::

    .. tab-item:: Program2 : step 2: program for server.c

        * There are many functions used in socket. We can classify those functions based on functionalities.

                * Create Socket

                * Bind Socket

                * Recvfrom data_packet

                * Close socket

        * ``socket()`` is used to create a new socket. For example,

        .. code-block:: c

                server_socket = socket(AF_INET, SOCK_RAW, IPPROTO_TCP);                    

        * ``bind()`` is used to associate the socket with a specific address and port. For example,

        .. code-block:: c
                
                ret = bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));

	* ``recvfrom`` is commonly used with sockets, where communication is connectionless. it provides information about the source (sender) of the data, including the sender's IP address and port number. For example,

        .. code-block:: c

                len  = recvfrom(server_socket, buffer, sizeof(buffer), 0, NULL, NULL);

        * ``close`` is used to close the socket To free up system resources associated with the socket. For example,

        .. code-block:: c

                (void)close(server_socket);

        * See the full program below,

        .. literalinclude:: multiple_data_transfer/server/server.c
                :language: c
                :emphasize-lines: 71, 72, 73, 85, 86, 87, 99, 100, 111

.. _program2_ipv4_raw_af_inet_tcp_socket_server_side_compile_and_execute:

.. tab-set::

    .. tab-item:: Program2 : Step 3: Compile and Execute Server.c
        
        .. code-block:: c
                :emphasize-lines: 1, 3
                
                $ gcc -o server server.c

                $ sudo ./server 127.0.0.1

		IP Address: 127.0.0.1
		Server listening
		Received: _Hello from client!
		Received: _Hello from client!
		Received: _Hello from client!
		Received: _Hello from client!
		Received: _Hello from client!
		Received: _Hello from client!
		Received: _Hello from client!
		Received: _Hello from client!
		Received: _Hello from client!
		Received: _Hello from client!

.. _program2_ipv4_raw_af_inet_tcp_socket_client_sequence_diagram:

.. tab-set::

    .. tab-item:: Program2 : Step 4: Sequence Diagram for CLIENT.c
        
        .. plantuml::
        
           @startuml
	   !theme spacelab
           start
           :socket(AF_INET, SOCK_RAW, IPPROTO_TCP);
           :i = 0;
           while (while (i < NUM_MESSAGES)) is (yes)
           :sendto(client_socket, buffer + 3, sizeof(struct iphdr) + sizeof(struct tcphdr) + len, 0, (struct sockaddr*)&server_addr, sizeof(server_addr));
	   :++i;
           endwhile
           :(void)close(client_socket);
           stop
           @enduml
 
.. _program2_ipv4_raw_af_inet_tcp_socket_client_code: 

.. tab-set::

    .. tab-item:: Program2 : step 5: program for client.c

        * There are many functions used in socket. We can classify those functions based on functionalities.

                * Create Socket

                * Sendto data_packet

                * Close socket

        * ``socket`` is used to create a new socket. For example,

        .. code-block:: c

               client_socket = socket(AF_INET, SOCK_RAW, IPPROTO_TCP);

        * ``sendto`` is used to send the encoded message to the specified server address and port using a socket. For example,

        .. code-block:: c

		ret = sendto(client_socket, buffer + 3, sizeof(struct iphdr) + sizeof(struct tcphdr) + len, 0, (struct sockaddr*)&server_addr, sizeof(server_addr));

	* ``close`` is used to close the socket To free up system resources associated with the socket. For example,

        .. code-block:: c

                (void)close(server_socket);

        * See the full program below,
        
        .. literalinclude:: multiple_data_transfer/client/client.c
                :language: c
                :emphasize-lines: 98, 99, 100, 122, 123, 124, 125, 126, 127, 140

.. _program2_ipv4_raw_af_inet_tcp_socket_client_side_compile_and_execute:

.. tab-set::

    .. tab-item:: Program2 : Step 6: Compile and Execute Client.c
        
        .. code-block:: c
                :emphasize-lines: 1, 3

                $ gcc -o client client.c

                $ sudo ./client 127.0.0.1

		IP Address: 127.0.0.1
		Sentpacket: Hello from client!
		Sentpacket: Hello from client!
		Sentpacket: Hello from client!
		Sentpacket: Hello from client!
		Sentpacket: Hello from client!
		Sentpacket: Hello from client!
		Sentpacket: Hello from client!
		Sentpacket: Hello from client!
		Sentpacket: Hello from client!
		Sentpacket: Hello from client!


.. tab-set::

        .. tab-item:: Enhanced Socket Flexibility with ``AF_INET`` and ``PF_INET`` Domains

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                        **Default Domain:**

                                By default, the socket is configured to work in the ``AF_INET`` domain, handling all types of network data.

                        **Additional Domain Support:**

                                We expand the socket's capabilities to also function in the ``PF_INET`` domain, allowing it to operate similarly to ``AF_INET``.

                        **Socket Creation:**

                                We set up a network connection point known as a socket using ``socket(PF_INET, SOCK_RAW, IPPROTO_TCP)``.

                        **Working Scenario:**
                                
                                Despite the change in domain to ``PF_INET``, the socket continues to operate the same way, handling general network data.

.. _basic_example_ipv4_raw_af_inet_tcp_summary:

.. tab-set::

    .. tab-item:: Summary

        ============== ==================================================================================================================
        Socket API     Learning
        ============== ==================================================================================================================
        socket         Create a new socket
        recvfrom       It provides information about the source (sender) of the data, including the sender's IP address and port number. 
        sendto         Send the encoded message to the specified server address and port using a socket.
        ============== ==================================================================================================================

.. card:: See Also

        * Previous topic

                * :doc:`../../../sockets/ipv4_raw_af_inet_raw/epoll/epoll`

        * Current topic
                
                * :doc:`../../../sockets/ipv4_raw_af_inet_tcp/Basic_example/Basic_example`

        * Next topic
        
                * :doc:`../../../sockets/ipv4_raw_af_inet_tcp/select/select`

        * Other sockets
                
                * :doc:`../../../sockets/ipv4_raw_af_inet_udp`
                * :doc:`../../../sockets/ipv6_af_inet6_tcp`
                * :doc:`../../../sockets/ipv6_af_inet6_udp`
                * :doc:`../../../sockets/ipv6_raw_af_inet6_icmp`
                * :doc:`../../../sockets/ipv6_raw_af_inet6_tcp`
                * :doc:`../../../sockets/ipv6_raw_af_inet6_udp`
                * :doc:`../../../sockets/ipv6_raw_af_inet6_raw`
                * :doc:`../../../sockets/raw_af_packet_raw_htons_ETH_P_ALL`
                * :doc:`../../../sockets/raw_af_packet_tcp_htons_ETH_P_ALL`
                * :doc:`../../../sockets/raw_af_packet_udp_htons_ETH_P_ALL`

        * Other IPCs

                * :doc:`../../../Message_queues/Message_queues`
                * :doc:`../../../NamedPipes/NamedPipes`
                * :doc:`../../../Netlink/Netlink`
                * :doc:`../../../Shared_Memory/Shared_Memory`
                * :doc:`../../../Shared_Memory_2_FDS/Shared_Memory_2_FDS`
                * :doc:`../../../SocketPair/SocketPair`
                * :doc:`../../../Timerfd/Timerfd`