UDP Client Server Communication Using Sockets

Algorithms

Client

Step 1: Create Socket

• Create a UDP socket using socket(AF_INET, SOCK_DGRAM, 0).
• If socket creation fails, terminate the program.

Step 2: Define Server Address

• Set the address family to AF_INET.
• Set the port number to 5555.
• Set the IP address to 127.0.0.1.

Step 3: Get Input from User

• Read data from the user and store it in a buffer.

Step 4: Send Data to Server

• Send the data to the server using sendto().

Step 5: Receive Response

• Receive the response from the server using recvfrom().
• Display the received message.

Step 6: Close Socket

• Close the client socket.

Server

Step 1: Create Socket

• Create a UDP socket using socket(AF_INET, SOCK_DGRAM, 0).
• If socket creation fails, terminate the program.

Step 2: Define Server Address

• Set the address family to AF_INET.
• Set the port number to 5555.
• Set the IP address to 127.0.0.1.

Step 3: Bind Socket

• Bind the socket to the specified IP address and port using bind().

Step 4: Receive Data from Client

• Receive data from the client using recvfrom().
• Display the received message.

Step 5: Send Response to Client

• Send a confirmation message to the client using sendto().

Step 6: Close Socket

• Close the server socket.

Programs

Client

#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

int main() {
  char *ip = "127.0.0.1";
  int port = 5555;

  int sockfd;
  struct sockaddr_in addr;
  char buffer[1024];
  socklen_t addr_size;

  sockfd = socket(AF_INET, SOCK_DGRAM, 0);
  if (sockfd < 0) {
    perror("[-] Socket creation failed");
    exit(1);
  }
  printf("[CLIENT] UDP socket created\n");

  memset(&addr, 0, sizeof(addr));
  addr.sin_family = AF_INET;
  addr.sin_port = htons(port);
  addr.sin_addr.s_addr = inet_addr(ip);

  memset(buffer, 0, sizeof(buffer));
  printf("[CLIENT] Enter the data: ");
  scanf(" %[^\n]", buffer);

  sendto(sockfd, buffer, strlen(buffer), 0, (struct sockaddr *)&addr,
         sizeof(addr));
  printf("[CLIENT] Sent to server: %s\n", buffer);

  memset(buffer, 0, sizeof(buffer));
  addr_size = sizeof(addr);

  recvfrom(sockfd, buffer, sizeof(buffer), 0, (struct sockaddr *)&addr,
           &addr_size);
  printf("[CLIENT] Received from server: %s\n", buffer);

  close(sockfd);
  return 0;
}

Server

#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

int main() {
  char *ip = "127.0.0.1";
  int port = 5555;

  int sockfd;
  struct sockaddr_in server_addr, client_addr;
  char buffer[1024];
  socklen_t addr_size;
  int n;

  sockfd = socket(AF_INET, SOCK_DGRAM, 0);
  if (sockfd < 0) {
    perror("[-] Socket creation failed");
    exit(1);
  }
  printf("[SERVER] UDP socket created\n");

  memset(&server_addr, 0, sizeof(server_addr));
  server_addr.sin_family = AF_INET;
  server_addr.sin_port = htons(port);
  server_addr.sin_addr.s_addr = inet_addr(ip);

  n = bind(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr));
  if (n < 0) {
    perror("[-] Bind failed");
    exit(1);
  }
  printf("[SERVER] Bound to %s:%d\n", ip, port);

  memset(buffer, 0, sizeof(buffer));
  addr_size = sizeof(client_addr);

  recvfrom(sockfd, buffer, sizeof(buffer), 0, (struct sockaddr *)&client_addr,
           &addr_size);
  printf("[SERVER] Received from client: %s\n", buffer);

  strcpy(buffer, "Data successfully received");
  sendto(sockfd, buffer, strlen(buffer), 0, (struct sockaddr *)&client_addr,
         sizeof(client_addr));
  printf("[SERVER] Sent to client: %s\n", buffer);

  close(sockfd);
  return 0;
}