VxWorks本地UDP-server-C语言开发

UDP为应用程序提供了一种无需建立连接就可以发送封装的IP数据包的方法。UDP是OSI参考模型中一种无连接的传输层协议，它主要用于不要求分组顺序到达的传输中，分组传输顺序的检查与排序由应用层完成，提供面向事务的简单不可靠信息传送服务。UDP协议基本上是IP协议与上层协议的接口。UDP协议适用端口分别运行在同一台设备上的多个应用程序。
UDP提供了无连接通信，且不对传送数据包进行可靠性保证，适合于一次传输少量数据，UDP传输的可靠性由应用层负责。

UDP socket通信过程：

• 创建套接字
• 绑定套接字
• 收发数据
• 关闭套接字

UDP server

直接收发数据，不需要连接

#include "string.h"
#include "stdio.h"
#include "vxWorks.h"
#include "sockLib.h"
//#include "telnetLib.h"
#include "inetLib.h"
#include "stdioLib.h"
#include "strLib.h"
#include "hostLib.h"
#include "ioLib.h"

// 本地UDP server端口
#define LOCAL_SERVER_PORT 6666

// 缓冲buffer长度，最大message长度
#define BUFFER_SIZE 20480
#define MAX_MSG_LENGTH 20480
#define STRING_MAX_SIZE 20480

// 全局变量
char buffer[STRING_MAX_SIZE];
// UDP的网络通信对象
struct sockaddr_in local_udp_server_addr;

// UDP server 初始化
int udp_server_init(int port)
{
    int server_socket;

    /*创建套接字*/
    server_socket = socket(AF_INET, SOCK_DGRAM, 0);
    if (server_socket < 0)
    {
        printf("Create Socket Failed! \n");
        return -1;
    }

    // 填充server地址信息
    bzero((char *)&local_udp_server_addr, sizeof(local_udp_server_addr));
    local_udp_server_addr.sin_family = AF_INET;
    local_udp_server_addr.sin_addr.s_addr = htons(INADDR_ANY);
    local_udp_server_addr.sin_port = htons(port);

    // 绑定地址空间
    if (bind(server_socket, (struct sockaddr *)&local_udp_server_addr, sizeof(local_udp_server_addr)))
    {
        printf("Server Bind Port: %d Failed! \n", port);
        return -1;
    }

    return server_socket;
}

// UDP server 接收数据
void udp_server_receive_data(int server_socket)
{
    char receive_buffer[BUFFER_SIZE];
    int length;

    // 接受服务器返回的状态信息
    bzero(receive_buffer, BUFFER_SIZE);
    int len = sizeof(local_udp_server_addr);
    if ((length = recvfrom(server_socket, receive_buffer, MAX_MSG_LENGTH, 0, (struct sockaddr *)&local_udp_server_addr, &len)) == ERROR)
    {
        printf("Client Recieve Data Failed! \n");
        return;
    }

    bzero(buffer, STRING_MAX_SIZE);
    strncpy(buffer, receive_buffer, (strlen(receive_buffer) > STRING_MAX_SIZE ? STRING_MAX_SIZE : strlen(receive_buffer)));

    printf("receive data from client: %s \n", buffer);
}

// UDP server 发送数据
void udp_server_send_data(int server_socket)
{
    char send_buffer[BUFFER_SIZE];

    /* send request to server */
    bzero(send_buffer, BUFFER_SIZE);
    strncpy(send_buffer, buffer, strlen(buffer));
    int ret = sendto(server_socket, send_buffer, (strlen(send_buffer) + 1), 0, (struct sockaddr *)&local_udp_server_addr, sizeof(local_udp_server_addr));
    if (ret == ERROR)
    {
        printf("Send Data to Server Error! \n");
        return;
    }

    printf("send data to client: %s \n", send_buffer);
}

// 当前TCP通道结束条件：接收到OVER，关闭当前TCP通道
int finish_operation(int sock)
{
    char temp[BUFFER_SIZE];
    bzero(temp, BUFFER_SIZE);
    strncpy(temp, buffer, (strlen(buffer) > BUFFER_SIZE ? BUFFER_SIZE : strlen(buffer)));

    if (strcmp(temp, "END") == 0)
    {
        close(sock);
        return 1;
    }
    else
    {
        return 0;
    }
}

int main(void)
{
    // 初始化UDP server
    int udp_server_socket = udp_server_init(LOCAL_SERVER_PORT);
    if (udp_server_socket < 0)
    {
        return -1;
    }

    while (1)
    {
        udp_server_receive_data(udp_server_socket);
        udp_server_send_data(udp_server_socket);

        if (finish_operation(udp_server_socket))
        {
            break;
        }
    }

    // 异常结束，关闭socket
    close(udp_server_socket);

    return 0;
}