#include <arpa/inet.h> /*for struct sockaddr_in and INADDR_ANY*/
#include <netdb.h> /*for gethostbyname*/
#include <stdio.h> 
#include <sys/socket.h> /*for sockets*/
#include <sys/time.h> /*for timeval struct*/
#include <sys/types.h> /*for sockets and time*/
#include <unistd.h> /*read and time*/
#define MAX_BUFFER 16384

int main(int argc, char *argv[])
{
	char chrClientReadBuffer[MAX_BUFFER];
	char *chrRemoteHostIP;
	char chrRemoteHostReadBuffer[MAX_BUFFER];
	fd_set FileDescriptorSet;
	int intBlock;
	int intClientReadSize;
	int intClientSocket;
	int intHighestFD;
	int intRemoteHostReadSize;
	int intRemoteHostSocket;
	int intReuseOptval;
	int intServerSocket;
	struct hostent *RemoteHostNameAddress;
	struct sockaddr_in ClientSockAddress;
	struct sockaddr_in RemoteHostSockAddress;
	struct sockaddr_in ServerSockAddress;
	struct timeval timeSelectTimeout;
	unsigned int intClientAddressLength;
	unsigned short shrRemoteHostPort;
	unsigned short shrServerPort;
	
	if(argc < 3) {
	  printf("Usage: %s <Remote Host> <Remote Port> [Local Port]\n",argv[0]);
	  exit(0);
	}
	if (argc == 4)
		shrServerPort=atoi(argv[3]);
	else
		shrServerPort=5555;
	while(1) {
		if ((intServerSocket = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
			printf("Creating server socket failed\n");
			exit(0);
		}
		memset(&ServerSockAddress,'\0',sizeof(ServerSockAddress));
		ServerSockAddress.sin_family=AF_INET;
		ServerSockAddress.sin_addr.s_addr=htonl(INADDR_ANY);
		ServerSockAddress.sin_port=htons(shrServerPort);
		intReuseOptval=1;
		if ((setsockopt(intServerSocket, SOL_SOCKET, SO_REUSEADDR, &intReuseOptval, sizeof(intServerSocket))) < 0) {
			printf("setsockopt failed\n");
			exit(0);
		}
		if (bind(intServerSocket, (struct sockaddr *) &ServerSockAddress, sizeof(ServerSockAddress)) < 0) {
			printf("bind failed\n");
			exit(0);
		}
		if (listen(intServerSocket, 5) < 0) {
			printf("listen failed\n");
			exit(0);
		}
		intClientAddressLength=sizeof(ClientSockAddress);
		if ((intClientSocket=accept(intServerSocket, (struct sockaddr *) &ClientSockAddress, &intClientAddressLength)) < 0) {
			printf("accept failed\n");
			exit(0);
		}
		printf("Client %s connected\n",inet_ntoa(ClientSockAddress.sin_addr));
		if ((intRemoteHostSocket = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) {
			printf("Creating remote host socket failed\n");
			exit(0);
		}
		shrRemoteHostPort=atoi(argv[2]);
		chrRemoteHostIP=argv[1];
		if ((inet_aton(chrRemoteHostIP, &RemoteHostSockAddress.sin_addr)) == 0) {
			if ((RemoteHostNameAddress=gethostbyname(chrRemoteHostIP)) == NULL) {
				printf("gethostbyname failed\n");
				exit(0);
			}
			chrRemoteHostIP=inet_ntoa(*((struct in_addr *)RemoteHostNameAddress->h_addr));
		}
		memset(&RemoteHostSockAddress,'\0',sizeof(RemoteHostSockAddress));
		RemoteHostSockAddress.sin_family=AF_INET;
		RemoteHostSockAddress.sin_addr.s_addr=inet_addr(chrRemoteHostIP);
		RemoteHostSockAddress.sin_port=htons(shrRemoteHostPort);
		if (connect(intRemoteHostSocket, (struct sockaddr *) &RemoteHostSockAddress, sizeof(RemoteHostSockAddress)) < 0) {
			printf("connect failed\n");
			exit(0);
		}
		printf("Connected to %s on port %i\n",inet_ntoa(RemoteHostSockAddress.sin_addr),shrRemoteHostPort);
		memset(chrClientReadBuffer,'\0',sizeof(chrClientReadBuffer));
		memset(chrRemoteHostReadBuffer,'\0',sizeof(chrRemoteHostReadBuffer));
		intBlock=1;
		while(intBlock){
			timeSelectTimeout.tv_sec=0;
			timeSelectTimeout.tv_usec=1000;
			FD_ZERO(&FileDescriptorSet);
			FD_SET(intClientSocket, &FileDescriptorSet);
			FD_SET(intRemoteHostSocket, &FileDescriptorSet);
			intHighestFD = intClientSocket > intRemoteHostSocket ? intClientSocket + 1 : intRemoteHostSocket + 1;
			select(intHighestFD+1, &FileDescriptorSet, NULL, NULL, &timeSelectTimeout);
			if FD_ISSET(intClientSocket, &FileDescriptorSet) {
				if ((intClientReadSize=read(intClientSocket, chrClientReadBuffer, MAX_BUFFER)) > 0) {
					if ((write(intRemoteHostSocket, chrClientReadBuffer, intClientReadSize)) < 0) {
						printf("write to Remote Host Socket failed.\n");
						exit(0);
					}
					printf("Client Read: %s", chrClientReadBuffer);
					intClientReadSize = 0;
					memset(chrClientReadBuffer,'\0',sizeof(chrClientReadBuffer));
				}
			}
			if FD_ISSET(intRemoteHostSocket, &FileDescriptorSet) {
				if ((intRemoteHostReadSize=read(intRemoteHostSocket, chrRemoteHostReadBuffer, MAX_BUFFER)) >= 0) {
					if ((write(intClientSocket, chrRemoteHostReadBuffer, intRemoteHostReadSize)) < 0) {
						printf("write to Client Socket failed.\n");
						exit(0);
					}
					if (intRemoteHostReadSize == 0) {
						intBlock = 0;
						close(intClientSocket);
						close(intRemoteHostSocket);
						close(intServerSocket);
					}
					printf("Remote Host Read: %s", chrRemoteHostReadBuffer);
					//intRemoteHostReadSize = 0;
					memset(chrRemoteHostReadBuffer,'\0',sizeof(chrRemoteHostReadBuffer));
				}
			}
		}
	}
}