Client Initialization and Receive Thread

C

typedef struct {
    struct sockaddr_in serverAddr;
    int socket;
} Client;
 
Client client;
 
void *receiveMessages(void *arg) {
    char buffer[MAX_MESSAGE_SIZE];
    ssize_t bytesRead;
 
    while (1) {
        bytesRead = recvfrom(client.socket, buffer, sizeof(buffer), 0, NULL, NULL);
        if (bytesRead == -1) {
            perror("Receive failed");
            exit(EXIT_FAILURE);
        }
 
        buffer[bytesRead] = '\0';
        printf("Server: %s", buffer);
    }
}

Client Structure Definition: A structure (Client) is defined to hold information about the server address and the client socket.
Client Initialization: An instance of the Client structure (client) is created to store client-related information.
Receive Thread Function: The receiveMessages function is defined to handle continuous message reception from the server in a separate thread.

Step 3: Socket Creation and Message Sending

C

int main() {
    pthread_t receiveThread;
    char message[MAX_MESSAGE_SIZE];
    ssize_t bytesRead;
 
    // Create socket
    if ((client.socket = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
        perror("Socket creation failed");
        exit(EXIT_FAILURE);
    }
 
    // Configure server address
    memset(&client.serverAddr, 0, sizeof(client.serverAddr));
    client.serverAddr.sin_family = AF_INET;
    client.serverAddr.sin_port = htons(PORT);
    if (inet_aton("127.0.0.1", &client.serverAddr.sin_addr) == 0) {
        perror("Invalid server address");
        exit(EXIT_FAILURE);
    }
 
    // Create a thread to receive messages
    pthread_create(&receiveThread, NULL, receiveMessages, NULL);
 
    // Send and receive messages
    while (1) {
        // Get user input
        printf("Enter message: ");
        fgets(message, sizeof(message), stdin);
 
        // Send message to server
        sendto(client.socket, message, strlen(message), 0, (struct sockaddr*)&client.serverAddr, sizeof(client.serverAddr));
    }
 
    close(client.socket);
 
    return 0;
}

Socket Creation: A UDP socket is created using the socket system call.
Server Address Configuration: The server address is configured with the server’s IP, port, and protocol details.
Thread Creation: A thread (receiveThread) is created to run the receiveMessages function concurrently.
Message Sending Loop: Inside an infinite loop, the client continuously prompts the user for input, sends the message to the server using sendto, and then repeats the process.
Socket Closure: When the program terminates, the client socket is closed using close.

Step 4: Receive Thread Function

C

void *receiveMessages(void *arg) {
    char buffer[MAX_MESSAGE_SIZE];
    ssize_t bytesRead;
 
    while (1) {
        bytesRead = recvfrom(client.socket, buffer, sizeof(buffer), 0, NULL, NULL);
        if (bytesRead == -1) {
            perror("Receive failed");
            exit(EXIT_FAILURE);
        }
 
        buffer[bytesRead] = '\0';
        printf("Server: %s", buffer);
    }
}

Thread Function Definition: The receiveMessages function continuously receives messages from the server using recvfrom.
Buffer Initialization: A buffer (buffer) is used to store the received message.
Error Handling: If the reception fails, an error message is printed, and the program exits with an error status.
Message Printing: The received message is printed to the console with a prefix indicating it’s from the server.

Step 5: Write the Entire Code

Now, write the entire code in the client.c which is stated below in the code block.

C

#include <arpa/inet.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#define PORT 8888
#define MAX_MESSAGE_SIZE 1024
 
typedef struct {
    struct sockaddr_in serverAddr;
    int socket;
} Client;
 
Client client;
 
void* receiveMessages(void* arg)
{
    char buffer[MAX_MESSAGE_SIZE];
    ssize_t bytesRead;
 
    while (1) {
        bytesRead = recvfrom(client.socket, buffer,
                             sizeof(buffer), 0, NULL, NULL);
        if (bytesRead == -1) {
            perror("Receive failed");
            exit(EXIT_FAILURE);
        }
 
        buffer[bytesRead] = '\0';
        printf("Server: %s", buffer);
    }
}
 
int main()
{
    pthread_t receiveThread;
    char message[MAX_MESSAGE_SIZE];
    ssize_t bytesRead;
 
    // Create socket
    if ((client.socket = socket(AF_INET, SOCK_DGRAM, 0))
        == -1) {
        perror("Socket creation failed");
        exit(EXIT_FAILURE);
    }
 
    // Configure server address
    memset(&client.serverAddr, 0,
           sizeof(client.serverAddr));
    client.serverAddr.sin_family = AF_INET;
    client.serverAddr.sin_port = htons(PORT);
    if (inet_aton("127.0.0.1", &client.serverAddr.sin_addr)
        == 0) {
        perror("Invalid server address");
        exit(EXIT_FAILURE);
    }
 
    // Create a thread to receive messages
    pthread_create(&receiveThread, NULL, receiveMessages,
                   NULL);
 
    // Send and receive messages
    while (1) {
        // Get user input
        printf("Enter message: ");
        fgets(message, sizeof(message), stdin);
 
        // Send message to server
        sendto(client.socket, message, strlen(message), 0,
               (struct sockaddr*)&client.serverAddr,
               sizeof(client.serverAddr));
    }
 
    close(client.socket);
 
    return 0;
}

Client Script Code

How to create a multi-chat server using UDP?

In this article, we will see the development of a Multi-Threaded UDP Chat Server-Client Network for Data Transfer in Linux. UDP is used for low latency and connectionless characteristics, the architecture consists of a server managing multiple clients through threading. This networked chat application facilitates real-time communication, allowing users to exchange messages seamlessly. We will create the Server and Client script and perform live execution of communication between the server and multiple clients.

Tags:

#Geeks Premier League 2023 #Geeks Premier League #Linux-Unix

Creating Client Script

Steps to Execute Scripts

Client Initialization and Receive Thread

C

Step 3: Socket Creation and Message Sending

C

Step 4: Receive Thread Function

C

Step 5: Write the Entire Code

C

How to create a multi-chat server using UDP?

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