Supongamos que tengo una página web en un servidor Apache corriendo en 192.168.1.1:80 y quiero acceder a él desde 127.0.0.1:8080 (las ip y puertos son solo de ejemplo).

El siguiente programa me muestra la página pero las imágenes no cargan, tampoco puedo hacer login. No se que es lo que tengo mal.

// g++ -Wall -Werror tcp_proxy.cpp -o tcp_proxy -lpthread -lws2_32
 
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <pthread.h>
#include <winsock2.h>
#include <ws2tcpip.h>
 
#define Localhost "127.0.0.1"
#define ProxyPort 8080
#define HTTP_Server "192.168.1.1"
#define HTTP_Port "80"
 
#define MaxUsersQueue 10
#define MaxMsgSize 2048
 
struct sockets {
	int source;
	int dest;
};
 
void* conectarProxy(void*);
void* pushData(void*);
 
int main(int argc, char* argv[]) {
	WSADATA wsaData;
	WSAStartup(MAKEWORD(2, 2), &wsaData);
 
	int proxy_socket = socket(AF_INET, SOCK_STREAM, 0);
 
	sockaddr_in server_addr;
	server_addr.sin_family = AF_INET;
	server_addr.sin_addr.s_addr = inet_addr(Localhost);
	if (argc < 2)
		server_addr.sin_port = htons(ProxyPort);
	else // Usar puerto pasado desde la terminal
		server_addr.sin_port = htons(atoi(argv[1]));
 
	int server_addr_size = sizeof(server_addr);
	bind(proxy_socket, (sockaddr*) &server_addr, server_addr_size);
 
	listen(proxy_socket, MaxUsersQueue);
 
	while (true) {
		sockaddr_in client_addr;
		int client_addr_size = sizeof(client_addr);
		int socket_client = accept(proxy_socket, (sockaddr*) &client_addr, &client_addr_size);
 
		pthread_t hilo_conectarProxy;
		pthread_create(&hilo_conectarProxy, NULL, conectarProxy, &socket_client);
	}
	close(proxy_socket);
	return 0;
}
 
void* conectarProxy(void* sc_param) {
	int socket_client = *((int*)sc_param);
 
	int httpServerSock = socket(AF_INET, SOCK_STREAM, 0);
	addrinfo hints;
	memset(&hints, 0, sizeof(hints));
	hints.ai_family = AF_INET;
	hints.ai_socktype = SOCK_STREAM;
	addrinfo* res;
	getaddrinfo(HTTP_Server, HTTP_Port, &hints, &res);
	connect(httpServerSock, res->ai_addr, res->ai_addrlen);
	freeaddrinfo(res);
 
	sockets* cliente_proxy = new sockets{socket_client, httpServerSock};
	pthread_t hilo_cliente_proxy;
	pthread_create(&hilo_cliente_proxy, NULL, pushData, cliente_proxy);
 
	sockets* proxy_cliente = new sockets{httpServerSock, socket_client};
	pthread_t hilo_proxy_cliente;
	pthread_create(&hilo_proxy_cliente, NULL, pushData, proxy_cliente);
 
	pthread_join(hilo_cliente_proxy, NULL);
	pthread_join(hilo_proxy_cliente, NULL);
	return NULL;
}
 
void* pushData(void* args) {
	sockets* src_dst = (sockets*)args;
	int src = src_dst->source;
	int dst = src_dst->dest;
	char* data = new char[MaxMsgSize];
	char buffer[MaxMsgSize];
	while (true) {
		strcpy(data, "");
		strcpy(buffer, "");
		int msg_size = 0;
		do {
			msg_size += recv(src, buffer, MaxMsgSize, 0);
			if (msg_size == 0) break;
			if (msg_size == -1) break;
			printf("%d->%d Recibido: %d bytes\n", src, dst, msg_size);
			strcat(data, buffer);
		} while (strchr(data, '\n') == NULL);
		if (msg_size == -1) break;
		int sent_msg_size = send(dst, data, msg_size, 0);
		printf("%d->%d Enviado: %d bytes\n", src, dst, msg_size);
		if (sent_msg_size == -1) break;
	}
	delete (sockets*)args;
	delete[] data;
	close(src);
	close(dst);
	return NULL;
}
 

Ok, encontre el error, las imagenes no terminan con un salto de linea. Primero se envia un HTTP request con el tamaño del archivo y luego los datos del archivo.

void* pushData(void* args) {
	sockets* src_dst = (sockets*)args;
	int src = src_dst->source;
	int dst = src_dst->dest;
	char* data = new char[1048576];
	while (true) {
		strcpy(data, "");
		int msg_size = recv(src, data, 1048576, 0);
		if (msg_size > 0) {
			printf("%d->%d Reenviando %d bytes\n", src, dst, msg_size);
			send(dst, data, msg_size, 0);
		}
	}
	delete (sockets*)args;
	delete[] data;
	close(src);
	close(dst);
	return NULL;
}