C++ 쓰레드 활용 클래스 오버라이딩 문제

class Socket : public UserSocket
{
public: void onConnection_request(const int fd, sockaddr_in addr) {}
public: Socket() : UserSocket("tcp") {}
}

#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <pthread.h>
 
class UserSocket
{
	public:
		//Call back events
		//콜백 이벤트
		void onData_receive(const int dataSize, const char *data){}
		void onClose(){}
		void onConnection_request(const int fd, const struct sockaddr_in addr){}
		void onAccept(){}
	private:
		//Essential attributes
		//필수 속성들
		int fd = -1; //소켓 번호
		struct sockaddr_in local_addr, remote_addr; //로컬, 상대 주소
		bool sendable = false; //데이터 전송 가능 여부
 
		//Event handlers
		//이벤트 핸들러들
		pthread_t th_listen = 0, th_read = 0;
	public:
		int getFd()
		{
			return fd;
		}
	private:
		static void *listen_thread_func(void *arg)
		{
			class UserSocket us = *(UserSocket*)arg;
			sockaddr_in remote_addr;
			int lst;
			unsigned int SZ_REMOTE_ADDR = sizeof(remote_addr);
			while(true)
			{
				lst = accept(us.getFd(),
						(struct sockaddr*)&remote_addr, &SZ_REMOTE_ADDR);
				if(lst < 0) break;
				us.onConnection_request(lst, remote_addr);
			}
		}
		bool start_listen_thread()
		{
			if(!isGood_to_use()) return false;
 
			if(pthread_create(&th_listen, NULL, listen_thread_func, (void*)this) < 0)
				return false;
			return true;
		}
		static void *receive_thread_func(void *arg)
		{
			class UserSocket us = *(UserSocket*)arg;
			int size;
			char buf[1500];
 
			while(true)
			{
				memset(buf, 0, sizeof(buf));
				size = read(us.getFd(), buf, sizeof(buf));
				if(size <= 0) break;
				us.onData_receive(size, buf);
			}
			us.disconnect();
		}
		bool start_receive_thread()
		{
			if(!isGood_to_use()) return false;
			if(pthread_create(&th_read, NULL, receive_thread_func, (void*)this) < 0)
				return false;
			return true;
		}
	public:
		void lower_str(char *x)
		{
			for(int i=0; x[i]!=0; i++)
			{
				if('A' <= x[i] && x[i] <= 'Z')
					x[i] += 32;
			}
		}
		UserSocket(const char *xProto)
		{
			char *strProto = new char[strlen(xProto) + 1];
			strcpy(strProto, xProto);
 
			int yProto = -1;
			lower_str(strProto);
			if(!strcmp("tcp", strProto))
				yProto = SOCK_STREAM;
			else if(!strcmp("udp", strProto))
				yProto = SOCK_DGRAM;
 
			if(yProto != -1)
				fd = socket(AF_INET, yProto, 0);
			delete strProto;
		}
		~UserSocket()
		{
			if(fd >= 0)
				close(fd);
			if(th_read != 0)
				pthread_join(th_read, NULL);
			if(th_listen != 0)
				pthread_join(th_listen, NULL);
		}
		bool isGood_to_use()
		{
			if(fd < 0) return false;
			return true;
		}
		bool bind_in(const unsigned short xPort)
		{
			if(!isGood_to_use()) return false;
 
			memset(&local_addr, 0, sizeof(local_addr));
			local_addr.sin_family = AF_INET;
			local_addr.sin_addr.s_addr = htonl(INADDR_ANY);
			local_addr.sin_port = htons(xPort);
 
			if(bind(fd, (struct sockaddr*)&local_addr, sizeof(local_addr)) < 0)
				return false;
			return true;
		}
		bool bind_in(const char *xAddr, const unsigned short xPort)
		{
			if(!isGood_to_use()) return false;
 
			memset(&local_addr, 0, sizeof(local_addr));
			local_addr.sin_family = AF_INET;
			local_addr.sin_addr.s_addr = inet_addr(xAddr);
			local_addr.sin_port = htons(xPort);
 
			if(bind(fd, (struct sockaddr*)&local_addr, sizeof(local_addr)) < 0)
				return false;
			return true;
		}
		bool listen_in()
		{
 
			if(!isGood_to_use()) return false;
 
			if(listen(fd, 5) < 0) return false;
			return start_listen_thread();
		}
		bool accept_in(const int xFd, const struct sockaddr_in xAddr)
		{
			fd = xFd;
			memcpy(&remote_addr, &xAddr, sizeof(sockaddr_in));
			if(start_receive_thread())
			{
				sendable = true;
				onAccept();
				return true;
			}
			return false;
		}
		bool getSendable()
		{
			return sendable;
		}
		bool sendData(const char *xData, unsigned int xLen)
		{
			if(!getSendable()) return false;
			if(write(fd, xData, xLen) < 0) return false;
			return true;
		}
		void disconnect()
		{
			if(!isGood_to_use()) return;
			close(fd); fd = -1;
			onClose();
		}
};