Basic example tcp server and client
===================================

.. tab-set::

    .. tab-item:: IPv4 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 listen a socket ?

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                * How to connect a socket ?

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                * How to accept 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>`_

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

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

                        * `recv <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_af_inet_tcp_single_data_transfer>` 	
			* :ref:`program 2: tcp single server and single client : multiple data transfer <ipv4_af_inet_tcp_multiple_data_transfer>` 	

.. _ipv4_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 AF_INET TCP SOCKET FAQs <basic_example_ipv4_af_inet_tcp_socket>`
                        	* :ref:`Program1 : Step 1: Sequence Diagram for SERVER.c <program1_ipv4_af_inet_tcp_socket_server_sequence_diagram>`
                        	* :ref:`Program1 : Step 2: Program for Server.c <program1_ipv4_af_inet_tcp_socket_server_code>`
                        	* :ref:`Program1 : Step 3: Compile and Execute Server.c <program1_ipv4_af_inet_tcp_socket_server_side_compile_and_execute>`
                        	* :ref:`Program1 : Step 4: Sequence Diagram for CLIENT.c <program1_ipv4_af_inet_tcp_socket_client_sequence_diagram>`
                        	* :ref:`Program1 : Step 5: Program for Client.c <program1_ipv4_af_inet_tcp_socket_client_code>`
                        	* :ref:`Program1 : Step 6: Compile and Execute Client.c <program1_ipv4_af_inet_tcp_socket_client_side_compile_and_execute>`
				* :ref:`Summary <basic_example_ipv4_af_inet_tcp_summary>`

.. _ipv4_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 AF_INET TCP SOCKET FAQs <basic_example_ipv4_af_inet_tcp_socket>`
                        	* :ref:`Program2 : Step 1: Sequence Diagram for SERVER.c <program2_ipv4_af_inet_tcp_socket_server_sequence_diagram>`
                        	* :ref:`Program2 : Step 2: Program for Server.c <program2_ipv4_af_inet_tcp_socket_server_code>`
                        	* :ref:`Program2 : Step 3: Compile and Execute Server.c <program2_ipv4_af_inet_tcp_socket_server_side_compile_and_execute>`
                        	* :ref:`Program2 : Step 4: Sequence Diagram for CLIENT.c <program2_ipv4_af_inet_tcp_socket_client_sequence_diagram>`
                        	* :ref:`Program2 : Step 5: Program for Client.c <program2_ipv4_af_inet_tcp_socket_client_code>`
                        	* :ref:`Program2 : Step 6: Compile and Execute Client.c <program2_ipv4_af_inet_tcp_socket_client_side_compile_and_execute>`
				* :ref:`Summary <basic_example_ipv4_af_inet_tcp_summary>`

.. _basic_example_ipv4_af_inet_tcp_socket:
        
.. tab-set::

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

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                        Let us answer few basic questions in this socket
                
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                        What does the AF_INET parameter represent in the socket() function call?
                        
                        .. dropdown:: See Answer
                                
                                Address Family for IPv4

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                        Why is SOCK_STREAM used as the second parameter in the socket() function call?

                        .. dropdown:: See Answer
                                
                                It indicates that the socket will use a reliable, connection-oriented communication (TCP).

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                        What is the default protocol for a TCP socket created with socket(AF_INET, SOCK_STREAM, ?? )?

                        .. dropdown:: See Answer
                                
                                IPPROTO_TCP
        
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                        What is the primary characteristic of TCP communication?

                        .. dropdown:: See Answer

                                Connection-oriented and reliable

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                        What does a return value of -1 indicate in socket functions?    

                        .. dropdown:: See Answer
                                
                                In many socket programming APIs, a return value of -1 usually indicates an error. 
                                Functions often set an error code that can be retrieved using perror (or an equivalent mechanism) to determine the specific nature of the error.
		
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                        Why might bind() or listen() fail in socket programming?

                        .. dropdown:: See Answer

                                bind() might fail if the specified address is already in use, or if the process lacks the necessary permissions.
                                listen() might fail if the socket is not bound, or the operating system limit for pending connections is reached.

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                        How should you handle errors when using accept() in socket programming?

                        .. dropdown:: See Answer

                                Check the return value and handle errors appropriately

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

                        .. dropdown:: See Answer

                                It detects issues such as network errors or closed connections.

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                        Can you use a TCP socket (SOCK_STREAM) for sending and receiving data concurrently between a client and server? 
                             
                        .. dropdown:: See Answer
                                
                                Yes, TCP sockets support bidirectional communication.

.. _program1_ipv4_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_STREAM, IPPROTO_TCP);
           :bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));
           :listen(server_socket, 5);
           :client_socket = accept(server_socket, (struct sockaddr *)&client_addr, &addr_size);
           :send(client_socket, buffer, strlen(buffer), 0);
	   :(void)close(client_socket);
           stop
           @enduml

.. _program1_ipv4_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

                * Listen Socket

                * Accept Socket

                * Send data_packet

                * Close socket

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

        .. code-block:: c

		server_socket = socket(AF_INET, SOCK_STREAM, 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));		

        * ``listen()`` is used to set up a socket to accept incoming connections. For example,

        .. code-block:: c
                
                ret = listen(server_socket, 5);

	* ``accept()`` is used in network programming on the server side to accept a connection request from a client. For example,

        .. code-block:: c
                
    		client_socket = accept(server_socket, (struct sockaddr*)&client_addr, &addr_size);   		

        * ``send`` is used in network programming to send data over a connected socket. For example,

        .. code-block:: c

                ret = send(client_socket, buffer, strlen(buffer), 0);
        
	* ``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/server.c
                :language: c
		:emphasize-lines: 62, 63, 64, 71, 72, 73, 81, 89, 90, 91, 99, 100, 112, 113
	 
.. _program1_ipv4_af_inet_tcp_socket_server_side_compile_and_execute:

.. tab-set::

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

                $ sudo ./server 8080

		Port: 8080
		Message sent: Hello from server!


.. _program1_ipv4_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_STREAM, IPPROTO_TCP);
           :connect(client_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));
           :recv(client_socket, buffer, BUFFER_SIZE, 0);
	   :(void)close(client_socket);
           stop
           @enduml
  
.. _program1_ipv4_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

                * Connect Socket

                * Recv data_packet

                * Close socket

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

        .. code-block:: c
                                     
    		client_socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);   		

	* ``connect`` is used in network programming to establish a connection from a client to a server. For example,

        .. code-block:: c

                ret = connect(client_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));     

        * ``recv`` is used in network programming to receive data from a connected socket. For example,

        .. code-block:: c
        
                ret = recv(client_socket, buffer, BUFFER_SIZE, 0); 

        * ``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.c
                :language: c
		:emphasize-lines: 81, 82, 83, 90, 91, 92, 100, 101, 112

.. _program1_ipv4_af_inet_tcp_socket_client_side_compile_and_execute:

.. tab-set::

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

                $ gcc -o client client.c

                $ sudo ./client 8080 127.0.0.1

		Port: 8080
		IP Address: 127.0.0.1
		received = Hello from server!

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                $ sudo ./server 8080 127.0.0.1

                $ sudo ./client 8080 127.0.0.1

                program to run with elevated privileges, listen on port 8080, and bind to the loopback address 127.0.0.1. 
                
                <port_number> <ip_address> decided by the user based on the connection.

.. _program2_ipv4_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_STREAM, IPPROTO_TCP);
           :bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));
           :listen(server_socket, 5);
           :client_socket = accept(server_socket, (struct sockaddr *)&client_addr, &addr_size);
	   :i = 0;
           while (while (i < NUM_MESSAGES)) is (yes)
           :send(client_socket, buffer, strlen(buffer), 0);
	   :recv(client_socket, buffer,sizeof(buffer), 0);
	   :++i;
	   endwhile
	   :(void)close(client_socket);
           stop
           @enduml

.. _program2_ipv4_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

                * Listen Socket

                * Accept Socket

                * Send data_packet
		
		* Recv data_packet

                * Close socket

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

        .. code-block:: c

		server_socket = socket(AF_INET, SOCK_STREAM, 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));		

        * ``listen()`` is used to set up a socket to accept incoming connections. For example,

        .. code-block:: c
                
                ret = listen(server_socket, 5);

	* ``accept()`` is used in network programming on the server side to accept a connection request from a client. For example,

        .. code-block:: c
                
    		client_socket = accept(server_socket, (struct sockaddr*)&client_addr, &addr_size);   		

        * ``send`` is used in network programming to send data over a connected socket. For example,

        .. code-block:: c

                ret = send(client_socket, buffer, strlen(buffer), 0);

	* ``recv``  is used in network programming to receive data from a connected socket. For example,

        .. code-block:: c

                ret = recv(client_socket, buffer, sizeof(buffer), 0);

	* ``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:: multiple_data_transfer/server.c
                :language: c
		:emphasize-lines: 57, 58, 59, 72, 73, 74, 82, 90, 91, 92, 105, 106, 118, 119, 132, 133	

.. _program2_ipv4_af_inet_tcp_socket_server_side_compile_and_execute:

.. tab-set::

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

                $ sudo ./server 8080

		Port: 8080
		Received: Message 1 from client!
		Received: Message 2 from client!
		Received: Message 3 from client!
		Received: Message 4 from client!
		Received: Message 5 from client!
		Received: Message 6 from client!
		Received: Message 7 from client!
		Received: Message 8 from client!
		Received: Message 9 from client!
		Received: Message 10 from client!

.. _program2_ipv4_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_STREAM, IPPROTO_TCP);
           :connect(client_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));
	   :i = 0;
           while (while (i < NUM_MESSAGES)) is (yes) 
	   :recv(client_socket, buffer, BUFFER_SIZE, 0);
	   :send(client_socket, buffer, strlen(buffer), 0);
	   :++i;
	   endwhile
	   :(void)close(client_socket);
           stop
           @enduml
  
.. _program2_ipv4_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

                * Connect Socket

                * Recv data_packet

		* Send data_packet

                * Close socket

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

        .. code-block:: c
                                     
    		client_socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);   		

	* ``connect`` is used in network programming to establish a connection from a client to a server. For example,

        .. code-block:: c

                ret = connect(client_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));     

        * ``recv`` is used in network programming to receive data from a connected socket. For example,

        .. code-block:: c
        
                ret = recv(client_socket, buffer, BUFFER_SIZE, 0); 

	* ``send`` is used in network programming to send data over a connected socket. For example,

        .. code-block:: c

                ret = send(client_socket, buffer, strlen(buffer), 0);

        * ``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:: multiple_data_transfer/client.c
                :language: c
		:emphasize-lines: 76, 77, 78, 91, 92, 93, 102, 103, 118, 119, 130

.. _program2_ipv4_af_inet_tcp_socket_client_side_compile_and_execute:

.. tab-set::

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

                $ gcc -o client client.c

                $ sudo ./client 8080 127.0.0.1

		Port: 8080
		IP Address: 127.0.0.1
		received : Message 1 from server!
		received : Message 2 from server!
		received : Message 3 from server!
		received : Message 4 from server!
		received : Message 5 from server!
		received : Message 6 from server!
		received : Message 7 from server!
		received : Message 8 from server!
		received : Message 9 from server!
		received : Message 10 from server!

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                $ sudo ./server 8080 127.0.0.1

                $ sudo ./client 8080 127.0.0.1

                program to run with elevated privileges, listen on port 8080, and bind to the loopback address 127.0.0.1. 
                
                <port_number> <ip_address> decided by the user based on the connection.

.. 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_STREAM, 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_af_inet_tcp_summary:

.. tab-set::

    .. tab-item:: Summary

        ============== ==========================================================
        Socket API     Learning
        ============== ==========================================================
        socket         Create a new socket
        bind           Associate the socket with a specific address and port
        listen         Set up a socket to accept incoming connections.
        connect        Establish a connection from a client to a server.
        accept         Server side to accept a connection request from a client.
        recv           Receive data from a connected socket.
        send           Send data over a connected socket.
        ============== ==========================================================

.. card:: See Also

        * Current topic
		
		* :doc:`../../../sockets/ipv4_af_inet_tcp/Basic_example/Basic_example`

	* Next topic
	
		* :doc:`../../../sockets/ipv4_af_inet_tcp/select/select`

	* Other sockets
		
		* :doc:`../../../sockets/ipv4_af_inet_udp`
                * :doc:`../../../sockets/af_unix_tcp`
                * :doc:`../../../sockets/af_unix_udp`
                * :doc:`../../../sockets/ipv4_raw_af_inet_icmp`
                * :doc:`../../../sockets/ipv4_raw_af_inet_raw`
                * :doc:`../../../sockets/ipv4_raw_af_inet_tcp`
                * :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`