tcp_half_duplex_client.c File Reference

Client-side implementation of TCP Half Duplex Communication More...

#include <netdb.h>
#include <netinet/in.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

Include dependency graph for tcp_half_duplex_client.c:

Macros
#define	PORT   8100
	For structures returned by the network database library - formatted internet addresses and port numbers For in_addr and sockaddr_in structures. More...

Functions
void	error ()
	Utility function used to print an error message to stderr. More...
int	main ()
	Main function. More...

Detailed Description

Client-side implementation of TCP Half Duplex Communication

Author

Nikhill Vombatkere

See also

tcp_half_duplex_server.c

The algorithm is based on the simple TCP client and server model. However, instead of the server only sending and the client only receiving data, the server and client can both send data but only one at a time. This is implemented by using a particular ordering of the send() and recv() functions. When one of the clients or servers is sending, the other can only receive and vice-versa. In this way, the Half Duplex Form of communication can be represented using the TCP server-client model & socket programming

Macro Definition Documentation

PORT

#define PORT   8100

For structures returned by the network database library - formatted internet addresses and port numbers For in_addr and sockaddr_in structures.

For specific bit size values of variables Variable types, several macros, and various functions for performing input and output Variable types, several macros, and various functions for performing general functions Various functions for manipulating arrays of characters For macro definitions related to the creation of sockets For definitions to allow for the porting of BSD programs For miscellaneous symbolic constants and types, and miscellaneous functions

Function Documentation

error()

void error

(

)

Utility function used to print an error message to stderr.

It prints str and an implementation-defined error message corresponding to the global variable errno.

Returns

void

{
    perror("Socket Creation Failed");
    exit(EXIT_FAILURE);
}

main()

int main

(

void

)

Main function.

Returns

0 on exit

Variable Declarations

< socket descriptors - Like file handles but for sockets

< basic structures for all syscalls and functions that deal with internet addresses. Structures for handling internet addresses

< Character arrays to read and store string data for communication

The TCP socket is created using the socket function.

AF_INET (Family) - it is an address family that is used to designate the type of addresses that your socket can communicate with

SOCK_STREAM (Type) - Indicates TCP Connection - A stream socket provides for the bidirectional, reliable, sequenced, and unduplicated flow of data without record boundaries. Aside from the bidirectionality of data flow, a pair of connected stream sockets provides an interface nearly identical to pipes.

0 (Protocol) - Specifies a particular protocol to be used with the socket. Specifying a protocol of 0 causes socket() to use an unspecified default protocol appropriate for the requested socket type.

Server Address Information

The bzero() function erases the data in the n bytes of the memory starting at the location pointed to, by writing zeros (bytes containing '\0') to that area.

We bind the server_addr to the internet address and port number thus giving our socket an identity with an address and port where it can listen for connections

htons - The htons() function translates a short integer from host byte order to network byte order

htonl - The htonl() function translates a long integer from host byte order to network byte order

These functions are necessary so that the binding of address and port takes place with data in the correct format

Connects the client to the server address using the socket descriptor This enables the two to communicate and exchange data

Communication between client and server

The bzero() function erases the data in the n bytes of the memory starting at the location pointed to, by writing zeros (bytes containing '\0') to that area. The variables are emptied and then ready for use

First the CLIENT receives the servers message and displays it (recv())

The CLIENT is then prompted to type in a message and send it to the server. (send())

The server and client can communicate till one of them exits the connection

Since the exchange of information between the server and client take place one at a time this represents HALF DUPLEX COMMUNICATION

Receive Message

Send Message

Close Socket

{
    /** Variable Declarations */
    uint32_t
        sockfd;  ///< socket descriptors - Like file handles but for sockets
    struct sockaddr_in
        server_addr;  ///< basic structures for all syscalls and functions that
                      /// deal with internet addresses. Structures for handling
                      /// internet addresses
    char serverResponse[10000],
        clientResponse[10000];  ///< Character arrays to read and store string
                                /// data for communication
 
    /**
     * The TCP socket is created using the socket function.
     *
     * AF_INET (Family) - it is an address family that is used to designate the
     * type of addresses that your socket can communicate with
     *
     * SOCK_STREAM (Type) - Indicates TCP Connection - A stream socket provides
     * for the bidirectional, reliable, sequenced, and unduplicated flow of data
     * without record boundaries. Aside from the bidirectionality of data flow,
     * a pair of connected stream sockets provides an interface nearly identical
     * to pipes.
     *
     * 0 (Protocol) - Specifies a particular protocol to be used with the
     * socket. Specifying a protocol of 0 causes socket() to use an unspecified
     * default protocol appropriate for the requested socket type.
     */
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
    {
        error();
    }
 
    /**
     * Server Address Information
     *
     * The bzero() function erases the data in the n bytes of the memory
     * starting at the location pointed to, by writing zeros (bytes
     * containing '\0') to that area.
     *
     * We bind the server_addr to the internet address and port number thus
     * giving our socket an identity with an address and port where it can
     * listen for connections
     *
     * htons - The htons() function translates a short integer from host byte
     * order to network byte order
     *
     * htonl - The htonl() function translates a long integer from host byte
     * order to network byte order
     *
     * These functions are necessary so that the binding of address and port
     * takes place with data in the correct format
     */
    bzero(&server_addr, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(PORT);
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
 
    printf("Client is running...\n");
 
    /**
     * Connects the client to the server address using the socket descriptor
     * This enables the two to communicate and exchange data
     */
    connect(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr));
 
    printf("Client is connected...\n");
 
    /**
     * Communication between client and server
     *
     * The bzero() function erases the data in the n bytes of the memory
     * starting at the location pointed to, by writing zeros (bytes
     * containing '\0') to that area. The variables are emptied and then
     * ready for use
     *
     * First the CLIENT receives the servers message and displays it (recv())
     *
     * The CLIENT is then prompted to type in a message and send it to the
     * server. (send())
     *
     * The server and client can communicate till one of them exits the
     * connection
     *
     * Since the exchange of information between the server and client take
     * place one at a time this represents HALF DUPLEX COMMUNICATION
     */
    while (1)
    {
        bzero(&serverResponse, sizeof(serverResponse));
        bzero(&clientResponse, sizeof(clientResponse));
 
        /// Receive Message
        recv(sockfd, serverResponse, sizeof(serverResponse), 0);
        printf("\nServer message: %s \n", serverResponse);
 
        /// Send Message
        printf("\nEnter message here: ");
        fgets(clientResponse, 10000, stdin);
        send(sockfd, clientResponse, strlen(clientResponse) + 1, 0);
    }
 
    /// Close Socket
    close(sockfd);
    printf("Client is offline...\n");
    return 0;
}

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