未解析的外部符号 LNK2019

Question

首先，我知道这个问题在这个网站上已经有很多了，但是我已经几乎查看了所有的问题，似乎找不到出错的原因。 这是在VS 2012中遇到的。谢谢。

//Socket.h
#pragma once

#include <iostream>
#include <WinSock2.h>

using namespace std;

const int STRLEN = 256;

class Socket
{
    protected:
        WSADATA wsaData;
        SOCKET mySocket;
        SOCKET myBackup;
        SOCKET acceptSocket;
        sockaddr_in myAddress;
    public:
        Socket();
        ~Socket();
        bool SendData( char* );
        bool RecvData( char*, int );
        void CloseConnection();
        void GetAndSendMessage();
};

class ServerSocket : public Socket
{
    public:
        void Listen();
        void Bind( int port );
        void StartHosting( int port );
};

class ClientSocket : public Socket
{
    public:
        void ConnectToServer( const char *ipAddress, int port );
};

这是Socket.cpp文件

//Socket.cpp


#include "stdafx.h"
#include "Socket.h"


Socket::Socket()
{
    if( WSAStartup( MAKEWORD(2, 2), &wsaData ) != NO_ERROR )
    {
        cerr<<"Socket Initialization: Error with WSAStartup\n";
        system("pause");
        WSACleanup();
        exit(10);
    }

    //Create a socket
    mySocket = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP );

    if ( mySocket == INVALID_SOCKET )
    {
        cerr<<"Socket Initialization: Error creating socket"<<endl;
        system("pause");
        WSACleanup();
        exit(11);
    }

    myBackup = mySocket;
}

Socket::~Socket()
{
    WSACleanup();
}

bool Socket::SendData( char *buffer )
{
    send( mySocket, buffer, strlen( buffer ), 0 );
    return true;
}

bool Socket::RecvData( char *buffer, int size )
{
    int i = recv( mySocket, buffer, size, 0 );
    buffer[i] = '\0';
    return true;
}

void Socket::CloseConnection()
{
    //cout<<"CLOSE CONNECTION"<<endl;
    closesocket( mySocket );
    mySocket = myBackup;
}

void Socket::GetAndSendMessage()
{
    char message[STRLEN];
    cin.ignore();//without this, it gets the return char from the last cin and ignores the following one!
    cout<<"Send > ";
    cin.get( message, STRLEN );
    SendData( message );
}

void ServerSocket::StartHosting( int port )
{
     Bind( port );
     Listen();
}

void ServerSocket::Listen()
{
    //cout<<"LISTEN FOR CLIENT..."<<endl;

    if ( listen ( mySocket, 1 ) == SOCKET_ERROR )
    {
        cerr<<"ServerSocket: Error listening on socket\n";
        system("pause");
        WSACleanup();
        exit(15);
    }

    //cout<<"ACCEPT CONNECTION..."<<endl;

    acceptSocket = accept( myBackup, NULL, NULL );
    while ( acceptSocket == SOCKET_ERROR )
    {
        acceptSocket = accept( myBackup, NULL, NULL );
    }
    mySocket = acceptSocket;
}

void ServerSocket::Bind( int port )
{
    myAddress.sin_family = AF_INET;
    myAddress.sin_addr.s_addr = inet_addr( "0.0.0.0" );
    myAddress.sin_port = htons( port );

    //cout<<"BIND TO PORT "<<port<<endl;

    if ( bind ( mySocket, (SOCKADDR*) &myAddress, sizeof( myAddress) ) == SOCKET_ERROR )
    {
        cerr<<"ServerSocket: Failed to connect\n";
        system("pause");
        WSACleanup();
        exit(14);
    }
}

void ClientSocket::ConnectToServer( const char *ipAddress, int port )
{
    myAddress.sin_family = AF_INET;
    myAddress.sin_addr.s_addr = inet_addr( ipAddress );
    myAddress.sin_port = htons( port );

    //cout<<"CONNECTED"<<endl;

    if ( connect( mySocket, (SOCKADDR*) &myAddress, sizeof( myAddress ) ) == SOCKET_ERROR )
    {
        cerr<<"ClientSocket: Failed to connect\n";
        system("pause");
        WSACleanup();
        exit(13);
    } 

}

这里是stdafx.h

#pragma once

#include "targetver.h"

#define WIN32_LEAN_AND_MEAN             // Exclude rarely-used stuff from Windows headers
// Windows Header Files:
#include <windows.h>

// C RunTime Header Files
#include <stdlib.h>
#include <malloc.h>
#include <memory.h>
#include <tchar.h>


// TODO: reference additional headers your program requires here
#include "Socket.h"

以下是我的错误信息:

1>------ Build started: Project: Client, Configuration: Debug Win32 ------
1>  stdafx.cpp
1>  Socket.cpp
1>  Client.cpp
1>  Generating Code...
1>Socket.obj : error LNK2019: unresolved external symbol __imp__accept@12 referenced in function "public: void __thiscall ServerSocket::Listen(void)" (?Listen@ServerSocket@@QAEXXZ)
1>Socket.obj : error LNK2019: unresolved external symbol __imp__bind@12 referenced in function "public: void __thiscall ServerSocket::Bind(int)" (?Bind@ServerSocket@@QAEXH@Z)
1>Socket.obj : error LNK2019: unresolved external symbol __imp__closesocket@4 referenced in function "public: void __thiscall Socket::CloseConnection(void)" (?CloseConnection@Socket@@QAEXXZ)
1>Socket.obj : error LNK2019: unresolved external symbol __imp__connect@12 referenced in function "public: void __thiscall ClientSocket::ConnectToServer(char const *,int)" (?ConnectToServer@ClientSocket@@QAEXPBDH@Z)
1>Socket.obj : error LNK2019: unresolved external symbol __imp__htons@4 referenced in function "public: void __thiscall ServerSocket::Bind(int)" (?Bind@ServerSocket@@QAEXH@Z)
1>Socket.obj : error LNK2019: unresolved external symbol __imp__inet_addr@4 referenced in function "public: void __thiscall ServerSocket::Bind(int)" (?Bind@ServerSocket@@QAEXH@Z)
1>Socket.obj : error LNK2019: unresolved external symbol __imp__listen@8 referenced in function "public: void __thiscall ServerSocket::Listen(void)" (?Listen@ServerSocket@@QAEXXZ)
1>Socket.obj : error LNK2019: unresolved external symbol __imp__recv@16 referenced in function "public: bool __thiscall Socket::RecvData(char *,int)" (?RecvData@Socket@@QAE_NPADH@Z)
1>Socket.obj : error LNK2019: unresolved external symbol __imp__send@16 referenced in function "public: bool __thiscall Socket::SendData(char *)" (?SendData@Socket@@QAE_NPAD@Z)
1>Socket.obj : error LNK2019: unresolved external symbol __imp__socket@12 referenced in function "public: __thiscall Socket::Socket(void)" (??0Socket@@QAE@XZ)
1>Socket.obj : error LNK2019: unresolved external symbol __imp__WSAStartup@8 referenced in function "public: __thiscall Socket::Socket(void)" (??0Socket@@QAE@XZ)
1>Socket.obj : error LNK2019: unresolved external symbol __imp__WSACleanup@0 referenced in function "public: __thiscall Socket::Socket(void)" (??0Socket@@QAE@XZ)
1>C:\Users\ajayp_000\documents\visual studio 2012\Projects\Client\Debug\Client.exe : fatal error LNK1120: 12 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

- Iowa15

---

你是否已将 Ws2_32.lib 添加到链接器/输入设置的附加依赖项中？ - drescherjm

不，我会尝试并回到这篇文章。 - Iowa15

你可以这样添加 - #pragma comment(lib, "Ws2_32.lib") - SChepurin

好的，谢谢，那解决了我的问题。如果你把它作为答案，我会选择它。 - Iowa15

Answer 1

问题在于您没有链接Ws2_32.lib库。要解决此问题，您可以将其添加到项目的链接器/输入设置的附加依赖项选项卡中。或者（如SChepurin在评论中指出的那样），您可以添加

#pragma comment(lib, "Ws2_32.lib")

将其链接到项目的源文件。

- drescherjm

---

我在Eclipse中遇到了同样的问题。如何解决？ - Chintan Patel

Eclipse是一个集成开发环境。你使用的编译器是什么？不过如果不是Visual Studio的话，我可能也帮不上忙。 - drescherjm

如何在CLion中链接ws2_32，如果您正在使用CMake，则也会有所帮助。 - 9 Guy

@9Guy 你这条评论真是值得一枚奖牌。 - Spray'n'Pray

@Spray'n'Pray我已经不知道这个问题是关于什么，或者是什么让我来到这里。但我很高兴我能帮到你哈哈 - 9 Guy

Answer 2

另一种方法是在Visual Studio中右键单击项目，然后进入以下路径，并在其中添加“Ws2_32.lib”。 链接器>输入>附加依赖项

- eliasetm

---

对于不熟悉Visual Studio和C++的人来说，这个答案非常有帮助！谢谢。 - Eagle

Answer 3

在项目属性页面中，在“链接器”->“输入”下，在链接器“附加依赖项”中添加runtimeobject.lib。

- yoel halb

Answer 4

尽管这是一个连接器错误，但如果您在“属性>配置属性>C/C++>代码生成>运行时库”中设置了错误的“运行时库”选项，问题也可能发生。

二进制和调用二进制都应该具有相同的值。

- 如果调用二进制中的属性是MTd，那么被调用二进制中应该是MTd。 - 如果调用二进制中的属性是MDd，那么被调用二进制中应该是MDd。

- Ganesh Kamath - 'Code Frenzy'