Winsock C++ Proxy - c++

Question

I'm trying to get this code to work:
#include <stdio.h>
#include <tchar.h>
#include <iostream>
#include <WinSock2.h>
#pragma comment( lib, "ws2_32.lib" )
#include <Windows.h>
using namespace std;
int port = 5012;
SOCKET listen_sock;
SOCKET client_sock;
char FR_recv_buf [1048576] = "";
char recv_buf [102400] = "";
int Receive();
int Listen();
//function to initialize winsock
bool InitializeWinsock()
{
WSADATA wsaData;
int iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if(iResult != 0)
{
cout << "WSAStartup failed with error: " << iResult << endl;
return false;
}
else
{
cout << "WSAStartup successfully initialized." << endl;
return true;
}
}
int ForwardResponse()
{
if (send(client_sock, FR_recv_buf, sizeof(FR_recv_buf), 0) == SOCKET_ERROR)
{
cout << "Forward Response: send() failed with error: " << WSAGetLastError() << endl;
closesocket(client_sock);
//WSACleanup();
return 0;
}
else
{
cout << "Forward Response: send() success.\n";
//go back to begginning again?
Receive();
//CreateThread(0,0,(LPTHREAD_START_ROUTINE)Receive, 0, 0 ,0);
}
}
//Function to parse hostname from http request
string ParseHostname(char * buf)
{
size_t pos;
//string to hold hostname substring
string hostname_t;
//copy request to string for easier parsing
string httpheader = buf;
pos = httpheader.find("Host: ");//find "Host: " line
hostname_t = httpheader.substr(pos + 6);//copy to substring, not including "Host: ", just the hostname
pos = hostname_t.find("\r\n");// find end of line
hostname_t.erase(pos);//erase the rest of the string which is unwanted
return hostname_t;
}
//Function to forward HTTP request from browser to webserver
int ForwardRequest()
{
int bytes_received;
SOCKADDR_IN Dest;
SOCKET frecv_sock;
hostent *Host;
//parse hostname from http request
string hostname = ParseHostname(recv_buf);
if((Host=gethostbyname(hostname.c_str()))==NULL)
{
DWORD dwError = WSAGetLastError();
if (dwError != 0)
{
if(dwError == WSAHOST_NOT_FOUND)
{
cout << "Host " << hostname.c_str() << " not found.\n";
WSACleanup();
return FALSE;
}
else if (dwError == WSANO_DATA)
{
cout << "No data record found.\n";;
WSACleanup();
return FALSE;
}
else
{
cout << "Function failed with error: " << dwError << endl;
WSACleanup();
return FALSE;
}
}
}
else
{
cout << "Successfully connected to host: " << hostname.c_str() << endl;
//privmsg(wsockdl.sock,sendbuf,curchan);
}
Dest.sin_family=AF_INET;
Dest.sin_port=htons(80);
memcpy(&Dest.sin_addr,Host->h_addr,Host->h_length);
// Create a SOCKET for connecting to server
if((frecv_sock = socket(AF_INET,SOCK_STREAM,0))==INVALID_SOCKET)
{
cout << "Forward Request: Error at socket(), error code: " << WSAGetLastError() << endl;
closesocket(frecv_sock);
WSACleanup();
return FALSE;
}
// Connect to server
if(connect( frecv_sock,(SOCKADDR*)&Dest,sizeof(Dest))==SOCKET_ERROR)
{
cout << "Forward Request: connect() failed, error code: " << WSAGetLastError() << endl;
closesocket( frecv_sock);
WSACleanup();
return FALSE;
}
//send intercepted request to server
if (send(frecv_sock, recv_buf, strlen(recv_buf), 0) == SOCKET_ERROR)
{
cout << "Forward Request: send() failed with error: " << WSAGetLastError() << endl;
closesocket(frecv_sock);
WSACleanup();
return 0;
}
else
{
cout << "Forward Request: send() success.\n";
}
//receive request from server
do{
bytes_received = recv(frecv_sock,FR_recv_buf,sizeof(FR_recv_buf),0);
if (bytes_received > 0){
strcat (FR_recv_buf, "\0");
cout << "Forward Request: recv() success. Bytes received: " << bytes_received << endl;
CreateThread(0, 0, (LPTHREAD_START_ROUTINE)ForwardResponse, 0 ,0 ,0);
//ForwardResponse();
}
else if ( bytes_received == 0 ){
cout << "Forward Request: Connection closed\n";
closesocket(frecv_sock);
}
else if ( bytes_received == SOCKET_ERROR){
cout << "Forward Request: recv() failed with error: " << WSAGetLastError() << endl;
closesocket(frecv_sock);
WSACleanup();
return 0;
}
}while (bytes_received > 0);
}
//Function to accept connection and receive data from browser
int Receive()
{
SOCKADDR_IN csin;
int csin_len = sizeof(csin);
int iResult;
//accept client connection
client_sock = accept(listen_sock , (LPSOCKADDR)&csin, &csin_len);//pauses here to wait for connection from client
if (client_sock == INVALID_SOCKET) {
cout << "accept failed with error: "<< WSAGetLastError() << endl;
closesocket(client_sock);
WSACleanup();
return 1;
}
else{
cout << "Client connection from IP: " << inet_ntoa(csin.sin_addr) << ":" << csin.sin_port << endl;
}
CreateThread(0, 0 , (LPTHREAD_START_ROUTINE)Receive, 0 , 0 ,0); //Start another thread to accept.
do {
iResult = recv(client_sock, recv_buf, sizeof(recv_buf), 0);
if (iResult == SOCKET_ERROR) {
closesocket(client_sock);
WSACleanup();
cout << "Receive: recv() failed with error: "<< WSAGetLastError() << endl;
}
else if (iResult > 0){
//null terminate receive buffer
//recv_buf[iResult] = '\0';
strcat(recv_buf, "\0");
cout <<"Receive: Bytes received: " << iResult << endl;
//forward HTTP request from browser to web server
cout << recv_buf << endl;
HANDLE pChildThread = CreateThread(0, 0 , (LPTHREAD_START_ROUTINE)ForwardRequest, 0 , 0 ,0);
WaitForSingleObject(pChildThread,60000); //Wait for connection between proxy and remote server
CloseHandle(pChildThread);
}
else if ( iResult == 0 ){
cout << "Receive: Connection closed\n";
}
}while ( iResult > 0 );
return 0;
}
//Function which listens for incoming connections to the proxy
int Listen()
{
SOCKADDR_IN local;
memset(&local,0,sizeof(local));
local.sin_family = AF_INET;
local.sin_port = htons(port);
local.sin_addr.s_addr = INADDR_ANY;
//create socket for listening to
listen_sock = socket(AF_INET, SOCK_STREAM, 0);
//bind function associates a local address with a socket.
if (bind(listen_sock, (LPSOCKADDR)&local, sizeof(local)) == 0)
{
if (listen(listen_sock, 10) == 0)
{
cout << "Listening on: " << port << endl;
}
else
{
cout << "Error listening on socket.\n";
}
}
else{
cout << "bind() failed with error: "<< WSAGetLastError() << endl;
}
//accept and start receiving data from broswer
CreateThread(0, 0 , (LPTHREAD_START_ROUTINE)Receive, 0 , 0 ,0);
return 0;
}
int CloseServer()
{
closesocket(client_sock);
WSACleanup();
return 1;
}
int _tmain(int argc, _TCHAR* argv[])
{
InitializeWinsock();
Listen();
cin.get();
return 0;
}
But it seems like the connection ends too early, or the recv() or send() functions fail. Nothing is displayed on my browser except that it couldn't connect. Can anyone spot the problem?

Answer 1

One major problem is that you only have one client socket. Each thread you create share the same client socket so if two connections are made before the first one is done, the first socket will be over-written with the second connection. Remember that threads share all memory in the process, including things like global variables.
Edit: Since you are using C++, why don't you encapsulate variables and functions in a class? And instead of allocating memory for buffers statically like you do, create them on the heap with new.
Edit 2
Simple multi-threaded server:
class Connection
{
public:
Connection()
: buffer(0), buffer_size(0)
{ }
void run(SOCKET sock);
privat:
SOCKET input_socket; // Socket we read from
SOCKET output_socket; // Socket we write to
char *buffer; // Buffer we read data into, and write data from
size_t buffer_size; // Total size of buffer (allocated memory)
size_t read_size; // Number of bytes read
void connect();
void recv();
void send();
};
void Connection::run(SOCKET sock)
{
input_socket = sock;
if (buffer == 0)
{
// Allocate buffer
}
// Connect to the real server
connect();
for (;;)
{
try
{
recv();
send();
}
catch (exception &e)
{
std::cerr << "Error: " << e.what() << '\n';
break;
}
}
// Clean up
delete [] buffer;
closesocket(output_socket);
closesocket(input_socket);
}
void Connection::recv()
{
// Read data into the buffer, setting "read_size"
// Like: read_size = recv(input_socket, buffer_size, 0);
// Throw exception on error (includes connection closed)
// NOTE: If error is WSAEWOULDBLOCK, set read_size to 0, don't throw exception
}
void Connection::send()
{
if (read_size > 0)
{
// Send data from the buffer
// Like: send(output_socket, buffer, read_size, 0))
// Throw exception on error
}
}
void Connection::connect()
{
// Connect to the real server
// Set the output_socket member variable
}
DWORD client_thread(LPVOID param)
{
SOCKET socket = (SOCKET) param;
// Make socket nonblocking
int mode = 1;
ioctlsocket(socket, FIONBIO, &mode)
// Main thread stuff
Connection connection;
connection.run(socket);
}
int main()
{
// Create master socket, and other initialization
for (;;)
{
SOCKET client_socket = accept(...);
CreateThread(0, 0 , (LPTHREAD_START_ROUTINE) client_thread,
(LPVOID) client_socket , 0 ,0);
}
// Clean up
}

Answer 2

Another major problem is that you are appending '\0' to the received buffer in the apparent expectation that send() will recognize it and stop sending from there, even though the size parameter to send() is sizeof(FR_recv_buf), which is what it will really respect. Another problem is that data items such as FR_recv_buf are instance variables instead of local variables, so you can't handle multuple concurrent connections.