#include	"unpthread.h"static void	*doit(void *);		/* each thread executes this function */intmain(int argc, char **argv){	int				listenfd, connfd;	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;		connfd = Accept(listenfd, cliaddr, &len);		Pthread_create(NULL, NULL, &doit, (void *) connfd);	}}static void *doit(void *arg){	Pthread_detach(pthread_self());	str_echo((int) arg);	/* same function as before */	Close((int) arg);		/* we are done with connected socket */	return(NULL);}