send() 调用仅适用于套接字中的 telnet

问题描述

我正在使用带有 C++ 的 Windows 套接字。在接下来的调用中，我试图向刚刚连接的套接字回复一条消息。

我尝试在 C++ 中使用虚拟客户端进行连接。它会连接但 recv() 不会收到任何东西。

然后我尝试使用 telnet，它立即生效，就像我想要的那样。

SOCKET s = accept(ls,(sockaddr*)&clientSin,&s_len);

            if (s == INVALID_SOCKET) {
                cerr << "Error in accept call: " << WSAGetLastError();
            }
            else {
                cout << "Connection accepted at,socket no. :" << s << endl;
                //adding to list of incoming sockets
                inactiveList.push_back(s);
                //send message to client requesting credentials
                char buff[10];
                
                // the character 'x' is a code to the client to provide the server with the credentials
                buff[0] = 'x';
                buff[1] = '\0';
                //send(s,buff,2,0);
                if (send(s,"From Vic: ",10,0) == INVALID_SOCKET)
                {
                    int errorcode = WSAGetLastError();
                    cerr << "send to client Failed: " << errorcode << endl;
                    closesocket(s);
                    continue;
                }
                Sleep(1000);
                if (send(s,0) == INVALID_SOCKET)
                {
                    int errorcode = WSAGetLastError();
                    cerr << "send to client Failed: " << errorcode << endl;
                    closesocket(s);
                    continue;
                }
                
            }

接收代码为：

tnb = 0;
    while ((nb = recv(s,&buff[tnb],LInesZ - tnb,0)) > 0)
    {
        tnb += nb;
    }
    /* If there was an error on the read,report it. */
    if (nb < 0)
    {
        printf("recv Failed: %d\n",WSAGetLastError());
        return 1;
    }
    if (tnb == 0)
    {
        printf("disconnect on recv");
    }
    /* Make the response NULL terminated and display it.  Using C output */
    printf("tnb = %d\n",tnb);
    buff[tnb] = '\0';
    puts(buff);

解决方法

接受我所有的评论并将其转化为答案。

我怀疑您的 recv 循环一直在继续，因为您没有发送足够的数据使其脱离循环。

改变这个：

while ((nb = recv(s,&buff[tnb],LINESZ - tnb,0)) > 0)
{
    tnb += nb;
}

为此：（请注意，我正在为数组 buff 分配 +1）

char buff[LINESZ+1]; // +1 for null terminator
buff[0] = '\0';
tnb = 0;
while (tnb < LINESZ)
{
    nb = recv(s,LINESZ-tnb,0);
    if (nb < 0)
    {
        printf("Error on socket: %d\n",(int)WSAGetLastError());
        break;
    }
    else if (nb == 0)
    {
        printf("Remote socket closed\n");
        break;
    }

    printf("Received: %d bytes\n",(int)nb);

    tnb += nb;
    buff[tnb] = '\0'; // null terminate the end of the buffer so it will print reliably
}