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[英]C++ Winsock client will not receive data from server, but with Putty client it works
[英]C++ Winsock Library Termination When connecting with Putty Client on 127.0.0.1
我正在尝试创建一个服务器客户端,一旦它工作,我可以将一个向量传递给它,并通过 ssh 像腻子一样将它发送到客户端程序。 问题是每当我尝试在 127.0.0.1:45000 上使用 putty 连接 raw 或 ssh 时,程序一旦连接就会终止。
这是我的代码:
#include <iostream>
#include <WS2tcpip.h>
#include <string>
#pragma comment (lib, "ws2_32.lib")
using namespace std;
void main()
{
// Initialize winsock
WSADATA wsData;
WORD ver = MAKEWORD(2, 2);
int wsOk = WSAStartup(ver, &wsData);
if (wsOk != 0)
{
cerr << "Can't Intitialze winsock! Quiting" << endl;
return;
}
// Create a socket to bind
SOCKET listening = socket(AF_INET, SOCK_STREAM, 0);
if (listening == INVALID_SOCKET)
{
cerr << "Can't create a socket! Quitting" << endl;
}
// Bind the socket to an ip address to the port
sockaddr_in hint;
hint.sin_family = AF_INET;
hint.sin_port = htons(45000);
hint.sin_addr.S_un.S_addr = INADDR_ANY; // could also use inet_pton
bind(listening, (sockaddr*)&hint, sizeof(hint));
// Tell winsock the socket is for listening
listen(listening, SOMAXCONN);
// Wait for connection
sockaddr_in client;
int clientSize = sizeof(client);
SOCKET clientSocket = accept(listening, (sockaddr*)&client, &clientSize);
char host[NI_MAXHOST]; //Clients remote name
char service[NI_MAXHOST]; // Service (port) the client is on
ZeroMemory(host, NI_MAXHOST);
ZeroMemory(service, NI_MAXHOST); // use mem set of linux
if (getnameinfo((sockaddr*)&client, sizeof(client), host, NI_MAXHOST, service, NI_MAXSERV, 0) == 0)
{
cout << host << " connected on port " << service << endl;
return;
}
else
{
inet_ntop(AF_INET, &client.sin_addr, host, NI_MAXHOST);
cout << host << " connected on port " <<
ntohs(client.sin_port) << endl;
return;
}
// Close listening socket
closesocket(listening);
// while loop; accept and echo message back to client
char buf[4096];
while (true)
{
ZeroMemory(buf, 4096);
// wait for client to send data
int bytesReceived = recv(clientSocket, buf, 4096, 0);
if (bytesReceived == SOCKET_ERROR)
{
cerr << "Error in recv(). Quitting" << endl;
break;
}
if (bytesReceived == 0)
{
cout << "Client Disconnected, bytes 0" << endl;
break;
}
// echo message back to client
send(clientSocket, buf, bytesReceived + 1, 0);
// Close the socket
}
closesocket(clientSocket);
// Shutdown winsock
WSACleanup();
}
我正在编写它并在 Visual Studio 2019 中编译。
这是我在尝试连接 ssh 选项或 raw 时从 Putty 收到的消息。
如果有人可以提供帮助,将不胜感激。 谢谢!
调用getnameinfo()
时,无论getnameinfo()
是成功还是失败,都会立即从main()
return
,而无需先调用closesocket()
。 这是 Putty 错误的根源。 每当客户端连接时,您都会明确退出您的应用程序,而不会通知客户端连接正在关闭。
更一般地说,如果accept()
成功(并且socket()
也是),您应该始终在返回的SOCKET
上调用closesocket()
,无论您的代码中发生什么其他事情(如果WSAStartup()
成功,则与WSACleanup()
相同)。
您的代码中还有其他几个错误:
main()
具有非int
返回类型是非法的(尽管一些编译器允许这样做,作为非标准扩展。不要依赖它。)。
如果socket()
失败,您将错过main()
的return
。
您没有检查bind()
、 listen()
、 accept()
或send()
上的错误。
如果您只打算accept()
1 个客户端,那么将积压工作设置为SOMAXCONN
是没有意义的。
调用send()
时可能存在缓冲区溢出。 想象一下,如果recv()
正好返回接收到的 4096 个字节。 bytesReceived + 1
个字节数发送回客户端将使 go 超出buf
数组的范围。
话虽如此,尝试更像这样的东西:
#include <iostream>
#include <WS2tcpip.h>
#include <string>
#pragma comment (lib, "ws2_32.lib")
using namespace std;
int main()
{
// Initialize winsock
WSADATA wsData;
WORD ver = MAKEWORD(2, 2);
int errCode = WSAStartup(ver, &wsData);
if (errCode != 0)
{
cerr << "Can't initialize winsock! Error " << errCode << ". Quitting" << endl;
return 0;
}
// Create a socket to bind
SOCKET listening = socket(AF_INET, SOCK_STREAM, 0);
if (listening == INVALID_SOCKET)
{
errCode = WSAGetLastError();
cerr << "Can't create listening socket! Error " << errCode << ". Quitting" << endl;
WSACleanup();
return 0;
}
// Bind the socket to an ip address to the port
sockaddr_in hint = {};
hint.sin_family = AF_INET;
hint.sin_port = htons(45000);
hint.sin_addr.s_addr = INADDR_ANY; // could also use inet_pton
if (bind(listening, (sockaddr*)&hint, sizeof(hint)) == SOCKET_ERROR)
{
errCode = WSAGetLastError();
cerr << "Can't bind listening socket! Error " << errCode << ". Quitting" << endl;
closesocket(listening);
WSACleanup();
return 0;
}
// Tell winsock the socket is for listening
if (listen(listening, 1) == SOCKET_ERROR)
{
errCode = WSAGetLastError();
cerr << "Can't open listening socket! Error " << errCode << ". Quitting" << endl;
closesocket(listening);
WSACleanup();
return 0;
}
// Wait for connection
sockaddr_in client;
int clientSize = sizeof(client);
SOCKET clientSocket = accept(listening, (sockaddr*)&client, &clientSize);
if (clientSocket == INVALID_SOCKET)
{
errCode = WSAGetLastError();
cerr << "Can't accept a client! Error " << errCode << ". Quitting" << endl;
closesocket(listening);
WSACleanup();
return 0;
}
char host[NI_MAXHOST]; //Clients remote name
char service[NI_MAXHOST]; // Service (port) the client is on
ZeroMemory(host, NI_MAXHOST);
ZeroMemory(service, NI_MAXHOST); // use mem set of linux
if (getnameinfo((sockaddr*)&client, clientSize, host, NI_MAXHOST, service, NI_MAXSERV, 0) == 0)
{
cout << host << " connected on port " << service << endl;
}
else
{
inet_ntop(AF_INET, &(client.sin_addr), host, NI_MAXHOST);
cout << host << " connected on port " << ntohs(client.sin_port) << endl;
}
// Close listening socket
closesocket(listening);
listening = INVALID_SOCKET;
// while loop; accept and echo message back to client
char buf[4096];
while (true)
{
// wait for client to send data
int bytesReceived = recv(clientSocket, buf, sizeof(buf), 0);
if (bytesReceived == SOCKET_ERROR)
{
errCode = WSAGetLastError();
cerr << "Error reading from client: " << errCode << ". Quitting" << endl;
break;
}
if (bytesReceived == 0)
{
cout << "Client Disconnected" << endl;
break;
}
// echo message back to client
char *ptr = buf;
int bytesToSend = bytesReceived;
do
{
int bytesSent = send(clientSocket, ptr, bytesToSend, 0);
if (bytesSent == SOCKET_ERROR)
break;
ptr += bytesSent;
bytesToSend -= bytesSent;
}
while (bytesToSend > 0);
if (bytesToSend != 0)
{
errCode = WSAGetLastError();
cerr << "Error writing to client: " << errCode << ". Quitting" << endl;
break;
}
}
// Close the client socket
closesocket(clientSocket);
// Shutdown winsock
WSACleanup();
return 0;
}
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