2 way TCP

 

Server Code

c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>  // For close() function

• #include <stdio.h>: Includes the standard input/output library necessary for functions like printf and fgets.
• #include <stdlib.h>: Includes the standard library header for functions like exit.
• #include <string.h>: Includes the string library header for functions like memset and strlen.
• #include <sys/socket.h>: Includes definitions for socket functions and structures.
• #include <netinet/in.h>: Includes constants and structures needed for internet domain addresses.
• #include <unistd.h>: Includes definitions for miscellaneous functions, including close.

c
#define PORT 8080

• Defines a constant PORT with the value 8080, which will be used as the port number for the server.

c
int main() {
    struct sockaddr_in server, client;
    char buff[100];
    int sid = socket(AF_INET, SOCK_STREAM, 0);

• int main() {: Entry point of the program.
• struct sockaddr_in server, client;: Declares structures to hold the server's and client's internet addresses.
• char buff[100];: Declares a buffer to store messages sent and received.
• int sid = socket(AF_INET, SOCK_STREAM, 0);: Creates a socket with:
  • AF_INET: Address family for IPv4.
  • SOCK_STREAM: Socket type for TCP.
  • 0: Default protocol for TCP.

c
    if (sid == -1) {
        printf("Error in socket creation\n");
        exit(1);
    }

• Checks if sid is -1, indicating an error in socket creation. If so, prints an error message and exits the program with status 1.

c
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons(PORT);

• server.sin_family = AF_INET;: Sets the address family to IPv4.
• server.sin_addr.s_addr = INADDR_ANY;: Binds the socket to all available network interfaces.
• server.sin_port = htons(PORT);: Sets the port number to 8080, converting it to network byte order using htons.

c
    if (bind(sid, (struct sockaddr*)&server, sizeof(server)) == -1) {
        printf("Error in bind\n");
        close(sid);
        exit(1);
    }

• Binds the socket to the address and port specified in the server structure. Checks if bind returns -1, indicating an error. If so, prints an error message, closes the socket, and exits the program.

c
    listen(sid, 5);

• Puts the socket into listening mode, ready to accept incoming connections. 5 specifies the maximum length of the queue of pending connections.

c
    socklen_t len = sizeof(client);
    int temp = accept(sid, (struct sockaddr*)&client, &len);

• socklen_t len = sizeof(client);: Initializes len to the size of the client structure.
• int temp = accept(sid, (struct sockaddr*)&client, &len);: Accepts an incoming connection. Returns a new socket descriptor (temp) for the connection. If accept returns -1, it indicates an error.

c
    if (temp == -1) {
        printf("Error in accept\n");
        close(sid);
        exit(1);
    }

• Checks if temp is -1, indicating an error in accepting the connection. If so, prints an error message, closes the listening socket, and exits the program.

c
    while (1) {
        memset(buff, 0, sizeof(buff));
        if (recv(temp, buff, sizeof(buff), 0) <= 0) {
            printf("Client disconnected\n");
            break;
        }
        printf("Client: %s\n", buff);

• while (1) {: Infinite loop for continuous communication.
• memset(buff, 0, sizeof(buff));: Clears the buffer.
• if (recv(temp, buff, sizeof(buff), 0) <= 0) {: Receives data from the client. If recv returns 0 or a negative value, it indicates the client has disconnected.
• printf("Client: %s\n", buff);: Prints the received message from the client.

c
        printf("Enter message to send: ");
        fgets(buff, sizeof(buff), stdin);
        if (send(temp, buff, strlen(buff), 0) == -1) {
            printf("Error in send\n");
            break;
        }
    }

• Prompts the user to enter a message to send to the client.
• fgets(buff, sizeof(buff), stdin);: Reads a line of input from the user into buff.
• if (send(temp, buff, strlen(buff), 0) == -1) {: Sends the message to the client. If send returns -1, it indicates an error.

c
    close(temp);
    close(sid);
    return 0;
}

• close(temp);: Closes the connection socket.
• close(sid);: Closes the listening socket.
• return 0;: Exits the program with status 0.

Client Code

c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>  // For close() function

• Similar header inclusions as the server code for necessary functions and structures.

c
#define PORT 8080

• Defines the port number 8080 to connect to the server.

c
int main() {
    struct sockaddr_in client;
    char buff[100];
    int sid = socket(AF_INET, SOCK_STREAM, 0);

• int main() {: Entry point of the program.
• struct sockaddr_in client;: Declares a structure to hold the client's internet address.
• char buff[100];: Declares a buffer to store messages sent and received.
• int sid = socket(AF_INET, SOCK_STREAM, 0);: Creates a socket with similar parameters as the server.

c
    if (sid == -1) {
        printf("Error in socket creation\n");
        exit(1);
    }

• Checks if sid is -1, indicating an error in socket creation. If so, prints an error message and exits the program.

c
    client.sin_family = AF_INET;
    client.sin_addr.s_addr = INADDR_ANY;
    client.sin_port = htons(PORT);

• client.sin_family = AF_INET;: Sets the address family to IPv4.
• client.sin_addr.s_addr = INADDR_ANY;: Specifies that the client can connect to any available network interface.
• client.sin_port = htons(PORT);: Sets the port number to 8080, converting it to network byte order using htons.

c
    if (connect(sid, (struct sockaddr*)&client, sizeof(client)) == -1) {
        printf("Error in connect\n");
        close(sid);
        exit(1);
    }

• Attempts to connect to the server. Checks if connect returns -1, indicating an error. If so, prints an error message, closes the socket, and exits the program.

c
    while (1) {
        printf("Enter message to send: ");
        fgets(buff, sizeof(buff), stdin);
        if (send(sid, buff, strlen(buff), 0) == -1) {
            printf("Error in send\n");
            break;
        }

• while (1) {: Infinite loop for continuous communication.
• Prompts the user to enter a message to send to the server.
• fgets(buff, sizeof(buff), stdin);: Reads a line of input from the user into buff.
• if (send(sid, buff, strlen(buff), 0) == -1) {: Sends the message to the server. If send returns -1, it indicates an error.

c
        memset(buff, 0, sizeof(buff));
        if (recv(sid, buff, sizeof(buff), 0) <= 0) {
            printf("Server disconnected\n");
            break;
        }
        printf("Server: %s\n", buff);
    }

• memset(buff, 0, sizeof(buff));: Clears the buffer.
• if (recv(sid, buff, sizeof(buff), 0) <= 0) {: Receives data from the server. If recv returns 0 or a negative value, it indicates the server has disconnected.
• printf("Server: %s\n", buff);: Prints the received message from the server.

c
    close(sid);
    return 0;
}

• close(sid);: Closes the socket.
• return 0;: Exits the program with status 0.

Summary

• The server sets up a listening socket and waits for client connections.
• Upon accepting a connection, it enters a loop to receive and send messages.
• The client creates a socket, connects to the server, and enters a loop to send and receive messages.
• Both the client and server handle errors and clean up resources by closing sockets before exiting.