send() 调用仅适用于套接字中的 telnet

Question

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

我尝试使用 C++ 中的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，它立即工作，正如我想要的那样。

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, "From Vic: ", 10, 0) == INVALID_SOCKET)
                {
                    int errorcode = WSAGetLastError();
                    cerr << "send to client failed: " << errorcode << endl;
                    closesocket(s);
                    continue;
                }
                
            }

recv 码是：

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);

Answer 1

把我所有的cmets变成一个答案。

我怀疑你的 recv 循环会永远持续下去，因为你没有发送足够的数据来让它跳出循环。

改变这个：

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

对此：（请注意，我为数组 buff 分配了 +1）

char buff[LINESZ+1]; // +1 for null terminator
buff[0] = '\0';
tnb = 0;
while (tnb < LINESZ)
{
    nb = recv(s, &buff[tnb], 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
}