修复Linux下"Operation now in progress"错误的方法

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

#define PORT 8080
#define BUFFER_SIZE 1024

int main() {
    int sockfd, new_socket;
    struct sockaddr_in address;
    int addrlen = sizeof(address);
    char buffer[BUFFER_SIZE] = {0};

    // 创建socket
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons(PORT);

    // 绑定socket
    if (bind(sockfd, (struct sockaddr *)&address, sizeof(address)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }

    // 监听连接
    if (listen(sockfd, 3) < 0) {
        perror("listen");
        exit(EXIT_FAILURE);
    }

    // 设置socket为非阻塞
    int flags = fcntl(sockfd, F_GETFL, 0);
    if (fcntl(sockfd, F_SETFL, flags | O_NONBLOCK) < 0) {
        perror("fcntl");
        exit(EXIT_FAILURE);
    }

    printf("Server listening on port %d...\n", PORT);

    // 接受连接
    if ((new_socket = accept(sockfd, (struct sockaddr *)&address, (socklen_t*)&addrlen))<0) {
        if (errno == EWOULDBLOCK || errno == EAGAIN) {
            printf("No pending connections\n");
        } else {
            perror("accept");
            exit(EXIT_FAILURE);
        }
    }

    if(new_socket > 0){
        printf("Connection accepted\n");
        // 使用select来等待数据
        fd_set readfds;
        FD_ZERO(&readfds);
        FD_SET(new_socket, &readfds);

        struct timeval timeout;
        timeout.tv_sec = 5;
        timeout.tv_usec = 0;

        int activity = select(new_socket + 1, &readfds, NULL, NULL, &timeout);

        if ((activity < 0) && (errno!=EINTR)) {
            perror("select error");
            printf("select error\n");
        }

        if (activity > 0) {
            if (FD_ISSET(new_socket, &readfds)) {
                // 接收数据
                ssize_t valread = recv(new_socket, buffer, BUFFER_SIZE, 0);
                if (valread > 0) {
                    printf("Received: %s\n", buffer);
                } else if (valread == 0) {
                    printf("Client disconnected\n");
                } else {
                    perror("recv");
                }
            }
        } else {
            printf("Timeout occurred\n");
        }
    }


    close(new_socket);
    close(sockfd);
    return 0;
}

ssize_t bytes_received;
while (1) {
    bytes_received = recv(sockfd, buffer, BUFFER_SIZE, 0);
    if (bytes_received < 0) {
        if (errno == EINTR) {
            // 被信号中断，重试
            continue;
        } else {
            perror("recv");
            break;
        }
    } else if (bytes_received == 0) {
        // 连接关闭
        printf("Connection closed by peer\n");
        break;
    } else {
        // 成功接收到数据
        printf("Received: %s\n", buffer);
        break;
    }
}