Proxy server using threads - Bad file descriptor error

[Stiletto]

Hello,
My program is a proxy server that uses a pre-defined thread pool in order to handle client requests. If the proxy gets HTTP 1.1 it changes it and sends the origin server HTTP 1.0 request.

I have a problem but I can't figure it out. When the web page starts to load, I get Bad file descriptor error from both read() (read client request) and write() (write response to client).
I've tried playing with closing the client socket and origin socket, but As far as I udnerstand, the problem is not there.
Here is my code, I'll appriciate it if someone can take a look at it.
Thanks in advance.

int handleHttpRequest(void* socketNum){
	char* response;	//Holds response
	char* request=readClientRequest(socketNum);	//Holds request
	
	if (request==NULL){
		response=composeHttpResponse(INTERNAL_SERVER_ERR);
		sendResponse(socketNum, response);
		closeAndDestroy(socketNum, 0, NULL, response, NULL, NULL);
		return 0;
	}
           .
           .
            //Some more code...
           .
           .
	//Send request to destination server
	struct sockaddr_in destSrvr;
	int destSrvrFd;
	
	//Create the socket
	if ((destSrvrFd=socket(AF_INET,SOCK_STREAM,0))==-1){
		response=composeHttpResponse(INTERNAL_SERVER_ERR);
		sendResponse(socketNum, response);
		closeAndDestroy(socketNum, 0, request, response, host, path);
    		return 0;
	}
    	
    	//Connection settings
	destSrvr.sin_family = AF_INET;		//use the Internet address family
	destSrvr.sin_port = htons(80);		//set port to 80
	destSrvr.sin_addr.s_addr = ((struct in_addr*)(hostInfo->h_addr))->s_addr;
	
	
	//Connect
	if (connect(destSrvrFd, (struct sockaddr*) &destSrvr, sizeof(destSrvr)) < 0){
		response=composeHttpResponse(INTERNAL_SERVER_ERR);
		sendResponse(socketNum, response);
		closeAndDestroy(socketNum, destSrvrFd, request, response, host, path);
    		return 0;
	}
	
	//Write client request to destination server
	int nbytes=0;
	while (nbytes < strlen(request))
		if ( (nbytes=write(destSrvrFd, request, strlen(request))) < 0){
			response=composeHttpResponse(INTERNAL_SERVER_ERR);
			sendResponse(socketNum, response);
			closeAndDestroy(socketNum, destSrvrFd, request, response, host, path);
			return 0;
		}
	
	//Read response from destination server
	const int BUFFER_SIZE=512;
	char rBuffer[BUFFER_SIZE];
	response=(char*)malloc(BUFFER_SIZE+1);
	
	if (response==NULL){
		response=composeHttpResponse(INTERNAL_SERVER_ERR);
		sendResponse(socketNum, response);
		closeAndDestroy(socketNum, destSrvrFd, request, response, host, path);
		return 0;
	}
			
	nbytes=0;
	if ((nbytes = read(destSrvrFd, rBuffer, BUFFER_SIZE)) < 0){
		response=composeHttpResponse(INTERNAL_SERVER_ERR);
		sendResponse(socketNum, response);
		closeAndDestroy(socketNum, destSrvrFd, request, response, host, path);
		return 0;
	}
	rBuffer[BUFFER_SIZE]='\0';
	strcpy(response,rBuffer);
	while (nbytes!=0){
		if ((nbytes = read(destSrvrFd, rBuffer, BUFFER_SIZE)) < 0){
			response=composeHttpResponse(INTERNAL_SERVER_ERR);
			sendResponse(socketNum, response);
			closeAndDestroy(socketNum, destSrvrFd, request, response, host, path);
			return 0;
		}
		rBuffer[BUFFER_SIZE]='\0';
		response=realloc(response, strlen(response) + BUFFER_SIZE+1);
		strcat(response,rBuffer);
	}
	
	//Write server response back to client
	//sendResponse(socketNum, response);
	nbytes=0;
	while (nbytes < strlen(request))
		if ( (nbytes=write(*(int*)socketNum, response, strlen(response))) < 0){
			response=composeHttpResponse(INTERNAL_SERVER_ERR);
			sendResponse(socketNum, response);
			closeAndDestroy(socketNum, destSrvrFd, request, response, host, path);
			return 0;
		}
	
	//Close connections with client and destination server and free memory
	closeAndDestroy(socketNum, destSrvrFd, request, response, host, path);
	
	return 0;
}

//Reads client request. Returns request on success, NULL otherwise
char* readClientRequest(void* socketNum){
	int fd=*(int*)socketNum, nbytes=0;
	const int BUFFER_SIZE=4096;
	char buf[BUFFER_SIZE+1];					//Reading buffer
	char* req=(char*)malloc(BUFFER_SIZE+1);		//Holds request

	if (req==NULL)
		return NULL;
	
	//Read request from client
	if ((nbytes = read(fd, buf, BUFFER_SIZE)) < 0){
		printf("%d\n", fd);
		perror("error: read \n"); return NULL;
	}
	
	buf[BUFFER_SIZE]='\0';
	strcpy(req,buf);
	while ( strstr(req,"\r\n\r\n")==NULL ){
		if ((nbytes = read(fd, buf, BUFFER_SIZE)) < 0){
			perror("error: read\n"); return NULL;
		}
		buf[BUFFER_SIZE]='\0';
		req=realloc(req, strlen(req) + BUFFER_SIZE);
		strcat(req,buf);
	}
	return req;
}

//Writes response and closes connection with client.
void sendResponse(void* socketNum, char* response){
	int fd=*(int*)socketNum, nbytes=0;
	
	while (nbytes < strlen(response))
		if ( (nbytes=write(fd, response, strlen(response))) < 0){
			perror("error: write\n"); exit(EXIT_FAILURE);
		}
}

[Stiletto]

Can't edit original post, so I'm posting again for an easier review. I've made some changes to the code so it will be more clear and simple to me. Now only read() gives an error.
How long should I read response from original server?

        //**All code above is valid and OK**

	//Write client request to destination server
	sendMsg(destSrvrFd,request);
	
	//Read response from destination server
	response=readMsgfromServer(destSrvrFd);
	
	//Write response back to client
	sendMsg(*(int*)socketNum,response);
	
	//Close connections with client and destination server and free memory
	closeAndDestroy(socketNum, destSrvrFd, request, response, host, path);
	
	return 0;

char* readMsgfromServer(int fd){
	int nbytes=0;
	const int BUFFER_SIZE=4096;
	char buf[BUFFER_SIZE+1];					//Reading buffer
	char* req=(char*)malloc(BUFFER_SIZE+1);		//Holds request
	
	if (req==NULL)
		return NULL;
	
	if ((nbytes = read(fd, buf, BUFFER_SIZE)) < 0){
		perror("error: read \n"); return NULL;
	}
	
	buf[BUFFER_SIZE]='\0';
	strcpy(req,buf);
	while ( nbytes!=0 ){
		if ((nbytes = read(fd, buf, BUFFER_SIZE)) < 0){
			perror("error: read\n"); return NULL;
		}
		buf[BUFFER_SIZE]='\0';
		req=realloc(req, strlen(req) + BUFFER_SIZE);
		strcat(req,buf);
	}
	printf("%d End of while - nbytes==0\n", fd);
	return req;
}