socket编程UDP

服务器端：

int sock;
char recvbuf[1024] = {0};
struct sockaddr_in peeraddr;
初始化：
sock = socket(PF_INET, SOCK_DGRAM, 0)

memset(&servaddr, 0, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(MYPORT);
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);

bind():
bind(sock, (struct sockaddr *)&servaddr, sizeof(servaddr))

recvfrom():
int recvfrom(int sockfd, void *buf,int buf_len,unsigned int flags,struct sockaddr *from,sock_len *fromlen);
功能：从UDP接收数据，返回实际接收的字节数，失败时返回－1

参数说明：
Sockfd:套接字描述符
buf:指向内存块的指针
buf_len:内存块大小，以字节为单位
flags:一般为0
from:远端的地址，IP地址和端口号
fromlen:远端地址长度
n = recvfrom(sock, recvbuf, sizeof(recvbuf), 0,(struct sockaddr *)&peeraddr, &peerlen);

sendto():
int sendto(int sockfd, const void *data, int data_len, unsigned int flags, struct sockaddr *remaddr,sock_lenremaddr_len)

功能：基于UDP发送数据报，返回实际发送的数据长度，出错时返回－1

参数说明：
sockfd:套接字描述符
data:指向要发送数据的指针
data_len:数据长度
flags:通常为0
remaddr:远端地址：IP地址和端口号
remaddr_len:地址长度

sendto(sock, recvbuf, n, 0,(struct sockaddr *)&peeraddr, peerlen);

关闭：
close(sock);

客户端:

int socket;
struct sockaddr_in servaddr;

初始化:
memset(&servaddr, 0, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(MYPORT);
//char* SERVERIP = “127.0.0.1”;
servaddr.sin_addr.s_addr = inet_addr(SERVERIP);

发送：
sendto(sock, sendbuf, strlen(sendbuf), 0, (struct sockaddr *)&servaddr, sizeof(servaddr));

接收：
ret = recvfrom(sock, recvbuf, sizeof(recvbuf), 0, NULL, NULL);

关闭:
close(socket);

实例：

服务器：

#include 
#include 
#include 
#include 
#include 

#define SERVER_PORT 8888
#define BUFF_LEN 1024

void handle_udp_msg(int fd)
{
    char buf[BUFF_LEN];  //接收缓冲区，1024字节
    socklen_t len;
    int count;
    struct sockaddr_in clent_addr;  //clent_addr用于记录发送方的地址信息
    while(1)
    {
        memset(buf, 0, BUFF_LEN);
        len = sizeof(clent_addr);
        count = recvfrom(fd, buf, BUFF_LEN, 0, (struct sockaddr*)&clent_addr, &len);  //recvfrom是拥塞函数，没有数据就一直拥塞
        if(count == -1)
        {
            printf("recieve data fail!\n");
            return;
        }
        printf("client:%s\n",buf);  //打印client发过来的信息
        memset(buf, 0, BUFF_LEN);
        sprintf(buf, "I have recieved %d bytes data!\n", count);  //回复client
        printf("server:%s\n",buf);  //打印自己发送的信息给
        sendto(fd, buf, BUFF_LEN, 0, (struct sockaddr*)&clent_addr, len);  //发送信息给client，注意使用了clent_addr结构体指针

    }
}


/*
    server:
            socket-->bind-->recvfrom-->sendto-->close
*/

int main(int argc, char* argv[])
{
    int server_fd, ret;
    struct sockaddr_in ser_addr; 

    server_fd = socket(AF_INET, SOCK_DGRAM, 0); //AF_INET:IPV4;SOCK_DGRAM:UDP
    if(server_fd < 0)
    {
        printf("create socket fail!\n");
        return -1;
    }

    memset(&ser_addr, 0, sizeof(ser_addr));
    ser_addr.sin_family = AF_INET;
    ser_addr.sin_addr.s_addr = htonl(INADDR_ANY); //IP地址，需要进行网络序转换，INADDR_ANY：本地地址
    ser_addr.sin_port = htons(SERVER_PORT);  //端口号，需要网络序转换

    ret = bind(server_fd, (struct sockaddr*)&ser_addr, sizeof(ser_addr));
    if(ret < 0)
    {
        printf("socket bind fail!\n");
        return -1;
    }

    handle_udp_msg(server_fd);   //处理接收到的数据

    close(server_fd);
    return 0;
}

客户端：

#include 
#include 
#include 
#include 
#include 

#define SERVER_PORT 8888
#define BUFF_LEN 512
#define SERVER_IP "172.0.5.182"


void udp_msg_sender(int fd, struct sockaddr* dst)
{

    socklen_t len;
    struct sockaddr_in src;
    while(1)
    {
        char buf[BUFF_LEN] = "TEST UDP MSG!\n";
        len = sizeof(*dst);
        printf("client:%s\n",buf);  //打印自己发送的信息
        sendto(fd, buf, BUFF_LEN, 0, dst, len);
        memset(buf, 0, BUFF_LEN);
        recvfrom(fd, buf, BUFF_LEN, 0, (struct sockaddr*)&src, &len);  //接收来自server的信息
        printf("server:%s\n",buf);
        sleep(1);  //一秒发送一次消息
    }
}

/*
    client:
            socket-->sendto-->revcfrom-->close
*/

int main(int argc, char* argv[])
{
    int client_fd;
    struct sockaddr_in ser_addr;

    client_fd = socket(AF_INET, SOCK_DGRAM, 0);
    if(client_fd < 0)
    {
        printf("create socket fail!\n");
        return -1;
    }

    memset(&ser_addr, 0, sizeof(ser_addr));
    ser_addr.sin_family = AF_INET;
    //ser_addr.sin_addr.s_addr = inet_addr(SERVER_IP);
    ser_addr.sin_addr.s_addr = htonl(INADDR_ANY);  //注意网络序转换
    ser_addr.sin_port = htons(SERVER_PORT);  //注意网络序转换

    udp_msg_sender(client_fd, (struct sockaddr*)&ser_addr);

    close(client_fd);

    return 0;
}