UDP客户端与服务器通讯，客户端recvfrome阻塞

Question

创建了一个UDP客户端与服务器，在通讯过程中发现客户端在第一次启动时会阻塞在recvfrom()函数，退出客户端重连之后就能正常通讯。

系统：Ubuntu 20.04
GCC版本：10.1.0

以下是代码：
server：

int main(int argc,char *atgv[])
{
    int sockfd;
    struct sockaddr_in server,client;
    char send_buf[100],read_buf[100];
    unsigned int len,length;
    int rev;
    time_t timep;

    sockfd = socket(AF_INET,SOCK_DGRAM,0);
    if(sockfd<0)
        {
            perror("socket error");
            return -1;
        }


        bzero(&server,sizeof(server));
        server.sin_family = AF_INET;
        server.sin_addr.s_addr=htons(INADDR_ANY);/
        server.sin_port =htons(8888);

        len = sizeof(struct sockaddr);

        if(bind(sockfd,(struct sockaddr *)&server,len)<0)
            {
                perror("bind error");
                return -2;
            }

        while(1)
        {
            rev=recvfrom(sockfd, read_buf,100, 0, (struct sockaddr *)&client, &length);
            if(rev<0)
                {
                    printf("recvfrom error\n");
                    close(sockfd);
                    return -3;
                }
            printf("rev len: %d\n",rev);
            printf("IP: 0x%x, PORT: %d\n",ntohl(client.sin_addr.s_addr),ntohs(client.sin_port));
            printf("recv_buf: %s\n",read_buf);

            timep=time(NULL); 
            snprintf(send_buf,sizeof(send_buf),"%s",ctime(&timep)); 

            sendto(sockfd, send_buf, strlen(send_buf), 0, (struct sockaddr *)&client, length); 
            printf("send_buf: %s\n",send_buf);

            bzero(&client,length);
            bzero(send_buf,100);
            bzero(read_buf,100);
        }

        close(sockfd);
        return 0;
}

client：

int main(int argc,char *atgv)
{
    int sockfd;
    struct sockaddr_in server,serv;
    int len,length, rv;
    char send_buf[100]="Hello, UDP!", read_buf[100];

    bzero(read_buf,100);

    sockfd = socket(AF_INET,SOCK_DGRAM,0);
    if(sockfd<0)
        {
            perror("socket error");
            return -1;
        }

        bzero(&server,sizeof(server));
        server.sin_family = AF_INET；
        inet_pton(AF_INET,"192.168.83.129", &server.sin_addr.s_addr)
        server.sin_port =htons(8888);

        length=sizeof(struct sockaddr_in);
        sendto(sockfd, send_buf ,strlen(send_buf), 0, (struct sockaddr *)&server, length);


        rv=recvfrom(sockfd, read_buf, 100 ,0, (struct sockaddr*)&serv, &len); 
        if(rv<0)
            {
                printf("recvfrom error\n");
                close(sockfd);
                return -3;
            }

            printf("read_buf is: %s\n",read_buf);

            close(sockfd);
            return 0;
}

运行结果：
server：

client：

试了很多次都是第一次连接会阻塞，
后面退出client再连就可以了，请问各位大神是哪里有问题？

Answer 1

https://blog.csdn.net/Swallow_he/article/details/86690828