如何在QNX上使用UDP套接字？

本示例代码展示了如何使用QNX操作系统上的UDP套接字进行网络通信。首先需要创建一个UDP套接字，然后绑定到本地IP地址和端口，并设置接收和发送缓冲区。接收方可以通过recvfrom函数等待接收来自指定IP地址和端口的数据包，发送方可以通过sendto函数将数据包发送到指定IP地址和端口。

#include <sys/select.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#define MAX_BUF_SIZE 1024
#define LOCAL_IP "127.0.0.1"
#define LOCAL_PORT 12345
#define REMOTE_IP "127.0.0.1"
#define REMOTE_PORT 54321

int main(void)
{
    int udp_sock;
    struct sockaddr_in local_addr, remote_addr;
    char send_buf[MAX_BUF_SIZE], recv_buf[MAX_BUF_SIZE];
    fd_set read_set;
    int ret;

    // 创建UDP套接字
    if ((udp_sock = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    // 绑定到本地IP地址和端口
    memset(&local_addr, 0, sizeof(local_addr));
    local_addr.sin_family = AF_INET;
    local_addr.sin_port = htons(LOCAL_PORT);
    local_addr.sin_addr.s_addr = inet_addr(LOCAL_IP);
    if (bind(udp_sock, (struct sockaddr *)&local_addr, sizeof(local_addr)) < 0)
    {
        perror("bind");
        exit(EXIT_FAILURE);
    }

    // 设置接收和发送缓冲区
    int opt_value = MAX_BUF_SIZE;
    if (setsockopt(udp_sock, SOL_SOCKET, SO_RCVBUF, &opt_value, sizeof(opt_value)) < 0)
    {
        perror("setsockopt for SO_RCVBUF");
        exit(EXIT_FAILURE);
    }
    if (setsockopt(udp_sock, SOL_SOCKET, SO_SNDBUF, &opt_value, sizeof(opt_value)) < 0)
    {
        perror("setsockopt for SO_SNDBUF");
        exit(EXIT_FAILURE);
    }

    // 发送数据包到指定IP地址和端口
    memset(&remote_addr, 0, sizeof(remote_addr));
    remote_addr.sin_family = AF_INET;
    remote_addr.sin_port = htons(REMOTE_PORT);
    remote_addr.sin_addr.s_addr = inet_addr(REMOTE_IP);
    sprintf(send_buf, "Hello, QNX from UDP!");
    if (sendto(udp_sock, send_buf, strlen(send_buf), 0, (struct sockaddr *)&remote_addr, sizeof(remote_addr)) < 0)
    {
        perror("sendto");
        exit(EXIT_FAILURE);
    }

    // 等待接收来自指定IP地址和端口的数据包
    FD_ZERO(&read_set);
    FD_SET(udp_sock, &read_set);
    ret = select(udp_sock + 1, &read_set, NULL, NULL, NULL);
    if (ret < 0)
    {
        perror("select");
        exit(EXIT_FAILURE);
    }
    else if (ret == 0)
    {
        printf("No data received within timeout!\n");
        exit(EXIT_FAILURE);
    }
    else
    {
        socklen_t addr_len = sizeof(remote_addr);
        int recv_len = recvfrom(udp_sock, recv_buf, MAX_BUF_SIZE, 0, (struct sockaddr *)&remote_addr, &addr_len);
        if (recv_len < 0)
        {
            perror("recvfrom");
            exit(EXIT_FAILURE);
        }
        else
        {
            recv_buf[recv_len] = '\0';
            printf("Received data: %s\n", recv_buf);
        }
    }

    close(udp_sock);

    return EXIT_SUCCESS;
}

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