c++ - 使用 Winsock 客户端在本地网络上出现错误 11004

Question

问题

我正在使用代码作为服务器连接到 Hercules HW 终端上的本地主机，它可以正常工作。

然后我尝试在另一台计算机上的本地网络上的另一台计算机上设置服务器。

消息错误是为 WSAGetLastError() 11004

怎么了？我就是想不通。

代码

使用 Winsock 的客户端代码是:

#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif

#include <string>
#include <iostream>
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <cstdlib>
#include <cstdio>
#include <time.h>


// Need to link with Ws2_32.lib, Mswsock.lib, and Advapi32.lib
#pragma comment (lib, "Ws2_32.lib")
#pragma comment (lib, "Mswsock.lib")
#pragma comment (lib, "AdvApi32.lib")


#define DEFAULT_BUFLEN 512
#define DEFAULT_PORT "2112"
#define DEFAULT_PROTO SOCK_STREAM

int main()
{
    char Buffer[128];
    // default to localhost
    char *server_name = "localhost";
    unsigned short port = atoi(DEFAULT_PORT);
    int retval, loopflag = 0;
    int i, loopcount, maxloop = -1;
    unsigned int addr;
    int socket_type = DEFAULT_PROTO;
    struct sockaddr_in server;
    struct hostent *hp;
    int first = 1;
    WSADATA wsaData;
    SOCKET  conn_socket;

    //    srand(time(NULL));
    if ((retval = WSAStartup(0x202, &wsaData)) != 0)
    {
        fprintf(stderr, "Client: WSAStartup() failed: Error %d\n", retval);
        WSACleanup();
        return -1;
    }
    else
        printf("Client: WSAStartup() is OK.\n");

    printf("Defina o nome ou IP do servidor[default = localhost]:\n");
    //    scanf( "%s" , Buffer );
    gets_s(Buffer);
    if (Buffer[0] != 0)
        server_name = Buffer;

    //    server_name = &Buffer;

    if (isalpha(server_name[0]))
    {   // server address is a name
        hp = gethostbyname(server_name);
    }
    else
    { // Convert nnn.nnn address to a usable one
        addr = inet_addr(server_name);
        hp = gethostbyaddr((char *)&addr, 4, AF_INET);
    }

    if (hp == NULL)
    {
        fprintf(stderr, "Client: Endereco IP nao identificado \"%s\": Error %d\n", server_name, WSAGetLastError());
        WSACleanup();
        exit(1);
    }
    else
        printf("Client: gethostbyaddr() esta OK.\n");
    memset(Buffer, 0, 128);
    printf("Defina a porta do server[default = 2112]:\n");
    gets_s(Buffer);
    if (Buffer[0] != 0)
        port = atoi(Buffer);

    memset(&server, 0, sizeof(server));
    memcpy(&(server.sin_addr), hp->h_addr, hp->h_length);
    server.sin_family = hp->h_addrtype;
    server.sin_port = htons(port);

    conn_socket = socket(AF_INET, socket_type, 0); /* Open a socket */
    if (conn_socket <0)
    {
        fprintf(stderr, "Client: Erro ao abrir o socket: Error %d\n", WSAGetLastError());
        WSACleanup();
        return -1;
    }
    else
        printf("Client: socket() esta OK.\n");

    printf("Client: Cliente conectando com: %s.\n", hp->h_name);

    conn_socket = socket(AF_INET, socket_type, 0); /* Open a socket */
    if (connect(conn_socket, (struct sockaddr*)&server, sizeof(server)) == SOCKET_ERROR)
    {
        fprintf(stderr, "Client: connect() falhou: Error %d\n", WSAGetLastError());
        WSACleanup();
        return -1;
    }
    else
        printf("Client: connect() esta OK.\n");

    loopcount = 0;
    return 0;
}

使用 Visual Basic 2015 编译，使用:Project > Properties > Configuration Properties > C/C++ > Preprocessor > Preprocessor Definitions

_WINSOCK_DEPRECATED_NO_WARNINGS
_CRT_SECURE_NO_WARNINGS

测试

• 使用 telnet 和 ping 在使用 Hercules HW 终端创建的另一台服务器上工作。
• 将 Hercules HW 终端用作计算机 A 上的客户端和计算机 B 上的服务器也可以，所以我认为这与我的代码有关。
• 使用 nmap -p 2112 192.168.1.134

结果是:

Nmap scan report for 192.168.1.134

Host is up (0.00s latency).



PORT     STATE SERVICE

2112/tcp open  kip

MAC Address: 00:19:BB:F7:48:29 (Hewlett Packard)



Nmap done: 1 IP address (1 host up) scanned in 3.31 seconds

Answer 1

来自 https://msdn.microsoft.com/en-us/library/windows/desktop/ms740668(v=vs.85).aspx

WSANO_DATA 11004

Valid name, no data record of requested type.The requested name is valid and was found in the database, but it does not have the correct associated data being resolved for. The usual example for this is a host name-to-address translation attempt (using gethostbyname or WSAAsyncGetHostByName) which uses the DNS (Domain Name Server). An MX record is returned but no A record—indicating the host itself exists, but is not directly reachable.

您的代码在 gethostbyaddr(...) 处失败。这是因为您路由器上的 DNS 没有您计算机的 DNS 记录。

有了地址、端口和协议(protocol)，您应该直接尝试用它连接到服务器。

此外，gethostbyaddr 已被弃用:参见 https://msdn.microsoft.com/en-us/library/windows/desktop/ms738521(v=vs.85).aspx

有关如何设置套接字以进行连接的引用，请参阅 http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html#connect

在 beej 的代码中，您会看到一个 getaddrinfo 调用。它支持如图所示的主机名或带点的 ip 字符串，因此您应该能够从示例中删除以下代码:

if (isalpha(server_name[0]))
{   // server address is a name
    hp = gethostbyname(server_name);
}
else
{ // Convert nnn.nnn address to a usable one
    addr = inet_addr(server_name);
    hp = gethostbyaddr((char *)&addr, 4, AF_INET);
}