C- Webserver中的Socket编程

Question

当涉及到套接字编程时，我是一个初学者。我目前正在尝试开发一个web服务器，可以从浏览器中为基本的GET和POST http请求提供服务。我使用我的笔记本电脑作为服务器和客户端。所以我的想法是，我应该能够在火狐中输入http://127.0.0.1:PORT/，我的web服务器应该能够连接到那个端口并开始交谈。

到目前为止，我写的代码似乎不起作用。我正在使用ConText和Cygwin，以便能够在Windows中运行和执行程序。我也从我正在使用的端口中删除了防火墙。但是，seem服务器似乎无法识别该连接。

你知道为什么吗？我附上了我到目前为止写的代码。任何帮助都将不胜感激。目前，程序还没有通过“侦听端口..”。我已经隔离了故障，似乎它卡住了我已经强调的声明。

/* Webserver Code  */

#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>             // for the use of inet_ntop()
#include <netinet/in.h>

#define PORT "1500"                // the port we will connect to
#define BACKLOG 10                 // how many pending connections the queue will hold

void *get_in_addr(struct sockaddr *sa);


int main (void) {

    int sockfd, new_fd=0;
    int status;
    struct addrinfo hints;
    struct addrinfo *servinfo;      
    struct sockaddr_storage their_addr;
    char s[INET6_ADDRSTRLEN];
    socklen_t addr_size;            

    FILE *errors;

    memset(&hints, 0, sizeof hints); 
    hints.ai_family = AF_UNSPEC;     
    hints.ai_socktype = SOCK_STREAM; 
    hints.ai_flags = AI_PASSIVE;     


    errors = fopen("Errors.txt", "w");
        fprintf(errors,"testing...\n");
    if(errors == NULL){
        fprintf(stderr, "Cant open output file\n");
    }
    if ((status = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
        fprintf(errors, "getaddrinfo error: %s\n", gai_strerror(status));
        exit(1);
    }

    // make a socket
    // socket() function returns a socket file descriptor called sockfd
    sockfd = socket(servinfo->ai_family, servinfo->ai_socktype, 0);

    // bind to the port we passed in to getaddrinfo()
    if((bind(sockfd, servinfo->ai_addr, servinfo->ai_addrlen))== -1) {
        fprintf(errors, "Binding Failed\n");
        exit(1);
    }                                   

    // listen on the port
    if((listen(sockfd, BACKLOG))== -1) {
      fprintf(errors, "Listening failed\n");
      exit(1);
    } else {
      printf("Listening on port...\n");
 }

    //now accept an incoming connection
    addr_size = sizeof(their_addr);
    **new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &addr_size)**;
 printf( "new_fd = %d\n", new_fd);
    if(new_fd == -1) {
      fprintf(errors, "Accepting failed\n");
      exit(1);
 } else {
  printf("The Accepting worked\n");
 }

     //Prints out the address of the connector
    inet_ntop(their_addr.ss_family, get_in_addr((struct sockaddr *)&their_addr), s, sizeof(s));
    printf("server: got connection from %s\n", s);
    fclose(errors);

 return 0;
}



// To obtain the client's information
void *get_in_addr(struct sockaddr *sa)
{
    if (sa->sa_family == AF_INET) {
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }

    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

Answer 1

getaddrinfo()可能会返回多个条目，包括IPv6条目。这可能是你的问题所在。

注意:在getaddrinfo()调用后，错误检查丢失。

如果您希望浏览器能够连接到"127.0.0.1:PORT"，您应该：

通过

• bind()连接到INADDR_LOOPBACK和端口，而不需要通过对getaddrinfo()的getaddrinfo()
• properly设置调用获得任何帮助，将ai_family设置为AF_INET (这样您就只有IPv4了)。

请注意，如果getaddrinfo()的第一个参数为NULL，则返回的地址将设置为INADDR/IN6ADDRANY，这意味着您的服务器也将接受来自外部的连接。要限制到localhost的连接，请将第一个参数设置为"localhost“，而不是NULL。

为了保存这段代码，下面是我的getaddrinfo()结果转储代码：

    struct addrinfo hints, *aires=0, *ai;
    int i;
    int rc;

    memset( &hints, 0, sizeof(hints) );
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;
    rc = getaddrinfo( "localhost", "1500", &hints, &aires );
    if (rc == 0) {
        for ( ai=aires, i=0; ai; ai=ai->ai_next, i++ ) {
            printf( "gai: ai[%d].ai_canonname = %s\n", i, ai->ai_canonname );
            printf( "gai: ai[%d].ai_flags     = %d\n", i, ai->ai_flags );
            printf( "gai: ai[%d].ai_family    = %d (%s)\n", i, ai->ai_family, get_family_name(ai->ai_family) );
            printf( "gai: ai[%d].ai_socktype  = %d\n", i, ai->ai_socktype );
            printf( "gai: ai[%d].ai_protocol  = %d (%s)\n", i, ai->ai_protocol, get_proto_name(ai->ai_protocol) );
            printf( "gai: ai[%d].ai_addrlen   = %d\n", i, (int)ai->ai_addrlen );

            if (ai->ai_family == AF_INET) {
                struct sockaddr_in *sa = (struct sockaddr_in *)ai->ai_addr;
                printf( "gai: ai[%d].ai_addr[IPv4].sin_family = %d (%s)\n", i, sa->sin_family, get_family_name(sa->sin_family) );
                printf( "gai: ai[%d].ai_addr[IPv4].sin_port   = %d\n", i, ntohs(sa->sin_port) );
                printf( "gai: ai[%d].ai_addr[IPv4].sin_addr   = %s\n",
                    i, inet_ntop(AF_INET, &sa->sin_addr, buf, sizeof(buf)) );
            } else if (ai->ai_family == AF_INET6) {
                struct sockaddr_in6 *sa = (struct sockaddr_in6 *)ai->ai_addr;
                printf( "gai: ai[%d].ai_addr[IPv6].sin6_family   = %d (%s)\n", i, sa->sin6_family, get_family_name(sa->sin6_family) );
                printf( "gai: ai[%d].ai_addr[IPv6].sin6_port     = %d\n", i, ntohs(sa->sin6_port) );
                printf( "gai: ai[%d].ai_addr[IPv6].sin6_flowinfo = %d\n", i, sa->sin6_flowinfo );

                printf( "gai: ai[%d].ai_addr[IPv6].sin6_addr     = %s\n",
                    i, inet_ntop(AF_INET6, &sa->sin6_addr, buf, sizeof(buf)) );

                printf( "gai: ai[%d].ai_addr[IPv6].sin6_scope_id = %d\n", i, sa->sin6_scope_id );
            } else {
                printf( "gai: ai[%d].ai_addr = %p\n", i, ai->ai_addr );
            }
            printf("\n");
        }
    } else {
        printf( "gai: failed (%d)\n", rc );
    }
    freeaddrinfo( aires );