#include	"unpthread.h"static void	*doit(void *);		/* each thread executes this function */intmain(int argc, char **argv){	int				listenfd, *iptr;	socklen_t		addrlen, len;	struct sockaddr	*cliaddr;	if (argc == 2)		listenfd = Tcp_listen(NULL, argv[1], &addrlen);	else if (argc == 3)		listenfd = Tcp_listen(argv[1], argv[2], &addrlen);	else		err_quit("usage: tcpserv01 [ <host> ] <service or port>");	cliaddr = Malloc(addrlen);	for ( ; ; ) {		len = addrlen;		iptr = Malloc(sizeof(int));		*iptr = Accept(listenfd, cliaddr, &len);		Pthread_create(NULL, NULL, &doit, iptr);	}}static void *doit(void *arg){	int		connfd;	connfd = *((int *) arg);	free(arg);	Pthread_detach(pthread_self());	str_echo(connfd);		/* same function as before */	Close(connfd);			/* we are done with connected socket */	return(NULL);}