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c - 创建自己的 Web 服务器时无法连接到 localhost

问题描述

我已经创建了 Web 服务器，并且我想对其进行测试。我在浏览器（Chrome，我也使用 macbook pro）中输入了https://localhost:8080/test.html 。浏览器显示 ERR_CONNECTION_REFUSED。

如果有人可以帮助我解释和解决这种情况，那将非常有帮助。我试过在 linux 和 macOS 环境下运行这个程序，它们都不起作用。我已经在网上搜索了很多类似的解决方案，但是没有一个可以解决我的问题。感谢你们。

我的代码在这里：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h> // just added
#include <netdb.h>//Network address and service translation
#include <arpa/inet.h> //For message type convertion
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <sys/signal.h>
#include <signal.h>
#include <errno.h>

#define BUFFSIZE 2048

// port number
int port_num = 8080;

void handle(int fd) {
    printf("handle function.\n");
    char buff[BUFFSIZE + 1];
    int bytes_read = read(fd, buff, BUFFSIZE);
    printf("bytes_read: %d\n", bytes_read);
    if (bytes_read <= 0) {
        fprintf(stderr, "connection failed, or read failed.\n");
    }
    printf("Msg: %s\n", buff);
    exit(1);
}

int main(int argc, char* argv[]){

    // make sure get the port num
    /*
    if (argc != 2) {
        fprintf(stderr, "Error: Improper number of arguments used\n");
        exit(1);
    }else {
        port_num = atoi(argv[1]);
    }
    */
    // setup socket
    struct sockaddr_in server_address, client_address;
    socklen_t client_address_length = sizeof(client_address);

    // socket file descriptor
    int fd_server, fd_client;

    char buf[BUFFSIZE];
    int on = 1;

    fd_server = socket(AF_INET, SOCK_STREAM, 0);
    if (fd_server < 0) {
        fprintf(stderr, "Error: socket set up failed.\n");
        exit(1);
    }

    // I don't know what is this
    setsockopt(fd_server, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(int));

    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(port_num);
    server_address.sin_addr.s_addr = INADDR_ANY;

    // binding
    if (bind(fd_server, (struct sockaddr *)&server_address, sizeof(server_address)) == -1) {
        fprintf(stderr, "Error: binding failed.\n");
        exit(1);
    }


    // listen 
    if (listen(fd_server, 10) == -1) {
        fprintf(stderr, "Error: socket listen failed.\n");
        exit(1);
    }

    while (1) {
        // accept

        fd_client = accept(fd_server, (struct sockaddr *)&client_address, &client_address_length);
        if (fd_client == -1) {
            fprintf(stderr, "Error: accept failed.\n");
            continue;
        }
        printf("connected...\n");
        int pid = fork();
        if (!fork()) {
            // child process
            close(fd_server);

            memset(buf, 0, 2048);
            read(fd_client, buf, 2047);
            printf("%s\n", buf);
            close(fd_client);
            printf("closing...\n");
            exit(0);
        }
        close(fd_client);
    }
    return 0;
}

在我点击 url ( https://localhost:8080/test.html ) 后，它会打印 在此处输入图像描述

标签： cwebserver

解决方案

两件事情：

  • 首先，您fork()在主循环中调用了两次，因此您为每个连接创建了两个子进程，同时您必须检查给定的值并存储在pid变量中。
  • 其次，您不知道为什么要调用setsockopts以重用套接字提供的地址……您是对的。在这里没用……我已经评论过了。

通过进行以下更改，我进行了第一次尝试：

     // I don't know what is this
-    setsockopt(fd_server, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(int));
+    // setsockopt(fd_server, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(int)); // indeed, you had better not to use it.

和

         printf("connected...\n");
         int pid = fork();
-        if (!fork()) {
+        if (!pid) { // check for the value of pid, not call fork() again.
             // child process
             close(fd_server);

在此之后，我得到这个输出：

[s000]lcu@Luiss-MacBook-Pro:~/so/59935716$ pru
connected...
connected...
GET / HTTP/1.1
Host: localhost:8080
Connection: keep-alive
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.130 Safari/537.36
Sec-Fetch-User: ?1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Sec-Fetch-Site: none
Sec-Fetch-Mode: navigate
Accept-Encoding: gzip, deflate, br
Accept-Language: es,en;q=0.9
Cookie: tocTree_ref-topic-group:ref-group-resources:ref-group-jdbc:ref-group-jdbcconnectionpools:ref-jdbcconnectionpoolnew1Text-hi=tocTree:ref-topic-group:ref-group-resources:ref-group-jdbc:ref-group-jdbcconnectionpools:ref-jdbcconnectionpoolnew1:ref-jdbcconnectionpoolnew1_link; tocTree-hi=tocTree:ref-topic-group:ref-group-configuration:ref-group-connectionservice; JSESSIONID=2d890f14dcdd285f478653a16a62; treeForm_tree-hi=treeForm:tree:resources:JDBC:connectionPoolResources


closing...
GET / HTTP/1.1
Host: localhost:8080
Connection: keep-alive
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.130 Safari/537.36
Sec-Fetch-User: ?1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Sec-Fetch-Site: none
Sec-Fetch-Mode: navigate
Accept-Encoding: gzip, deflate, br
Accept-Language: es,en;q=0.9
Cookie: tocTree_ref-topic-group:ref-group-resources:ref-group-jdbc:ref-group-jdbcconnectionpools:ref-jdbcconnectionpoolnew1Text-hi=tocTree:ref-topic-group:ref-group-resources:ref-group-jdbc:ref-group-jdbcconnectionpools:ref-jdbcconnectionpoolnew1:ref-jdbcconnectionpoolnew1_link; tocTree-hi=tocTree:ref-topic-group:ref-group-configuration:ref-group-connectionservice; JSESSIONID=2d890f14dcdd285f478653a16a62; treeForm_tree-hi=treeForm:tree:resources:JDBC:connectionPoolResources


closing...
connected...
GET / HTTP/1.1
Host: localhost:8080
Connection: keep-alive
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.130 Safari/537.36
Sec-Fetch-User: ?1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Sec-Fetch-Site: none
Sec-Fetch-Mode: navigate
Accept-Encoding: gzip, deflate, br
Accept-Language: es,en;q=0.9
Cookie: tocTree_ref-topic-group:ref-group-resources:ref-group-jdbc:ref-group-jdbcconnectionpools:ref-jdbcconnectionpoolnew1Text-hi=tocTree:ref-topic-group:ref-group-resources:ref-group-jdbc:ref-group-jdbcconnectionpools:ref-jdbcconnectionpoolnew1:ref-jdbcconnectionpoolnew1_link; tocTree-hi=tocTree:ref-topic-group:ref-group-configuration:ref-group-connectionservice; JSESSIONID=2d890f14dcdd285f478653a16a62; treeForm_tree-hi=treeForm:tree:resources:JDBC:connectionPoolResources


closing...

（如您所见，谷歌浏览器尝试对服务器进行三次连接尝试）

经过一些修改后，我对您的代码进行了以下更改，导致了这一点：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h> // just added
#include <netdb.h>//Network address and service translation
#include <arpa/inet.h> //For message type convertion
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <sys/signal.h>
#include <signal.h>
#include <errno.h>

#define BUFFSIZE 2048

// port number
int port_num = 8080;

void handle(int fd) {
    printf("handle function.\n");
    char buff[BUFFSIZE + 1];
    int bytes_read = read(fd, buff, BUFFSIZE);
    printf("bytes_read: %d\n", bytes_read);
    if (bytes_read <= 0) {
        fprintf(stderr, "connection failed, or read failed.\n");
    }
    printf("Msg: %s\n", buff);
    exit(1);
}

int main(int argc, char* argv[]){

    // make sure get the port num
    /*
    if (argc != 2) {
        fprintf(stderr, "Error: Improper number of arguments used\n");
        exit(1);
    }else {
        port_num = atoi(argv[1]);
    }
    */
    // setup socket
    struct sockaddr_in server_address, client_address;
    socklen_t client_address_length = sizeof(client_address);

    // socket file descriptor
    int fd_server, fd_client;

    char buf[BUFFSIZE];
    int on = 1;

    fd_server = socket(AF_INET, SOCK_STREAM, 0);
    if (fd_server < 0) {
        fprintf(stderr, "Error: socket set up failed.\n");
        exit(1);
    }

    // I don't know what is this
    // setsockopt(fd_server, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(int)); // indeed, you had better not to use it.

    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(port_num);
    server_address.sin_addr.s_addr = INADDR_ANY;

    // binding
    if (bind(fd_server, (struct sockaddr *)&server_address, sizeof(server_address)) == -1) {
        fprintf(stderr, "Error: binding failed.\n");
        exit(1);
    }


    // listen 
    if (listen(fd_server, 10) == -1) {
        fprintf(stderr, "Error: socket listen failed.\n");
        exit(1);
    }

    // accept
    while ((fd_client = accept(fd_server, (struct sockaddr *)&client_address, &client_address_length)) >= 0) {
        printf("connected...\n"); // do this only in the child process. Or flush stdout before forking...
        fflush(stdout); // so you get only one message (you flush the buffer before forking)
        int pid = fork();
        if (pid == 0) { // check for the value of pid, not call fork() again.
            // child process
            close(fd_server);  // good.

            memset(buf, 0, 2048);
            ssize_t n = read(fd_client, buf, sizeof buf);
            if (n > 0) {
                write(1, buf, n);  // better not consider it a null terminated string.
            }
            close(fd_client);
            printf("closing...\n");
            exit(EXIT_SUCCESS);
        }
        close(fd_client); // good.
    }

    fprintf(stderr, "Error: accept failed.\n");
    exit(EXIT_FAILURE);
}

我没有检查这个handle()函数，因为它没有在主代码中使用。

您将从此处获得此代码的不同版本。

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