winsock服务器故障排除

Question

我已经编写并编译了一个服务器程序，用于在屏幕上回显客户端应用程序键入的任何内容，代码如下所示。

/*Server */
#define _WIN32_WINNT 0x501
#include <iostream>
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
using namespace std;

const int winsock_version = 2;
#define PORT "3490"
#define MAX_NUM_CONNECTIONS 10

int main(void){

    WSADATA wsadata;

    if (WSAStartup(MAKEWORD(winsock_version,0),&wsadata) == 0){
        cout<<"-WSAStartup Initialized." << endl;

        struct addrinfo hints,*res;
        int sock_fd;

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

        if (getaddrinfo(NULL,PORT,&hints,&res) != 0){
            cout<<"-Call to getaddress was unsucceful." << endl;
        }

        if( (sock_fd = socket(res->ai_family,res->ai_socktype,res->ai_protocol)) == -1){
            cout<<"-Unable to Create socket." << endl;
        }

        if ( (bind(sock_fd, res->ai_addr, res->ai_addrlen)) != -1 ){
            cout<<"-binding successful." << endl;
        }

        if ( (listen(sock_fd,MAX_NUM_CONNECTIONS)) != -1){
            cout<<"-Listening for incoming connections." << endl;
        }
        //-------------------------------------------------------------

        struct sockaddr_storage incming_info;
        socklen_t sin_size;
        sin_size = sizeof incming_info;

        int new_fd;

        new_fd = accept(sock_fd, (struct sockaddr*)&incming_info,&sin_size);
        if (new_fd == -1){
            cout<<"-Accepting error." << endl;
        }
        if(new_fd == INVALID_SOCKET){
            cout<<"-INVALID SOCKET ERROR." << endl;
        }
        closesocket(new_fd);
        //-------------------------------------------------------------

        cout<<"Connected?" << endl;

        while(true){
            int ret_val;
            char buffer[128];
            ret_val = recv(new_fd,buffer,sizeof(buffer),0);
            if(ret_val == -1){
                cout<<"Receiving Error." << endl;
                break;
            }else if(ret_val == 0){
                cout<<"Connection has been closed!." << endl;
                break;
            }else{
                cout<<"---Server Echoeing what was recieved from client---" << endl;
                cout<<"Server: " << buffer << endl;

            }
            closesocket(new_fd);
        }
        cout<<"-Closing connection" << endl;

    }else{
        cout<<"-WSAStartup Initialization failed." << endl;
        if(WSACleanup()!=0){
            cout<<"-WSACleanup Successful." << endl;
        }else{
            cout<<"-WSACleanup Failed." << endl;
        }
    }
    return 0;
}

整个程序编译并运行，但是当我尝试使用putty并连接到端口3490上的localhost时，服务器死机了，并打印出"Receiving Error“。导致此问题的原因是什么？

Answer 1

在将新套接字接受到new_fd之后，立即对其调用closesocket (如下所示)。您不应该这样做，直到您完成接收。如果您想在此时关闭侦听器套接字，则应改为调用closesocket(sock_fd)。

  int new_fd;

    new_fd = accept(sock_fd, (struct sockaddr*)&incming_info,&sin_size);
    if (new_fd == -1){
        cout<<"-Accepting error." << endl;
    }
    if(new_fd == INVALID_SOCKET){
        cout<<"-INVALID SOCKET ERROR." << endl;
    }
    closesocket(new_fd);