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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#define SERVER_PORT 12001
#define REPLY_PORT 12002
#define BUFFER_SIZE 1024
void handle_receive(int recv_sockfd, struct sockaddr_in *client_addr,
socklen_t addr_len, char *buffer)
{
ssize_t recv_len;
recv_len = recvfrom(recv_sockfd, buffer, BUFFER_SIZE, 0,
(struct sockaddr *)client_addr, &addr_len);
if (recv_len < 0)
{
perror("recvfrom");
close(recv_sockfd);
exit(EXIT_FAILURE);
}
buffer[recv_len] = '\0'; // Null-terminate the received string
printf("Received packet from %s:%d\n", inet_ntoa(client_addr->sin_addr),
ntohs(client_addr->sin_port));
printf("Data: %s\n", buffer);
}
void handle_send(int send_sockfd, struct sockaddr_in *client_addr,
socklen_t addr_len, const char *message)
{
ssize_t sent_len;
sent_len = sendto(send_sockfd, message, strlen(message), 0,
(struct sockaddr *)client_addr, addr_len);
if (sent_len < 0)
{
perror("sendto");
close(send_sockfd);
exit(EXIT_FAILURE);
}
printf("Sent reply to %s:%d from port %d\n", inet_ntoa(client_addr->sin_addr),
ntohs(client_addr->sin_port), REPLY_PORT);
}
int main()
{
int recv_sockfd, reply_sockfd;
struct sockaddr_in server_addr, reply_addr, client_addr;
char buffer[BUFFER_SIZE];
socklen_t addr_len = sizeof(client_addr);
// Create a UDP socket for receiving on SERVER_PORT
if ((recv_sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
{
perror("socket");
exit(EXIT_FAILURE);
}
// Configure the server address for receiving
memset(&server_addr, 0, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = INADDR_ANY;
server_addr.sin_port = htons(SERVER_PORT);
// Bind the receiving socket to the server address
if (bind(recv_sockfd, (struct sockaddr *)&server_addr,
sizeof(server_addr)) < 0)
{
perror("bind");
close(recv_sockfd);
exit(EXIT_FAILURE);
}
// Create a UDP socket for replying on REPLY_PORT
if ((reply_sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
{
perror("socket");
close(recv_sockfd);
exit(EXIT_FAILURE);
}
// Configure the reply address for sending
memset(&reply_addr, 0, sizeof(reply_addr));
reply_addr.sin_family = AF_INET;
reply_addr.sin_addr.s_addr = INADDR_ANY;
reply_addr.sin_port = htons(REPLY_PORT);
// Bind the reply socket to the reply address
if (bind(reply_sockfd, (struct sockaddr *)&reply_addr, sizeof(reply_addr)) < 0)
{
perror("bind");
close(recv_sockfd);
close(reply_sockfd);
exit(EXIT_FAILURE);
}
printf("UDP server is listening on port %d for incoming packets and on port %d for replies\n",
SERVER_PORT, REPLY_PORT);
while (1)
{
// Handle incoming packets on SERVER_PORT
handle_receive(recv_sockfd, &client_addr, addr_len, buffer);
// Send "OK" reply to the client from REPLY_PORT
handle_send(reply_sockfd, &client_addr, addr_len, "OK");
}
// Close the sockets
close(recv_sockfd);
close(reply_sockfd);
return 0;
}
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