diff --git a/stio/lib/stio-prv.h b/stio/lib/stio-prv.h
index f33cb38..1d48c7c 100644
--- a/stio/lib/stio-prv.h
+++ b/stio/lib/stio-prv.h
@@ -103,6 +103,8 @@ struct stio_t
 extern "C" {
 #endif
 
+stio_errnum_t stio_syserrtoerrnum (int no);
+
 stio_sckhnd_t stio_openasyncsck (int domain, int type);
 void stio_closeasyncsck (stio_sckhnd_t sck);
 int stio_makesckasync (stio_sckhnd_t sck);
diff --git a/stio/lib/stio-tcp.c b/stio/lib/stio-tcp.c
index 03e2390..895379e 100644
--- a/stio/lib/stio-tcp.c
+++ b/stio/lib/stio-tcp.c
@@ -55,8 +55,7 @@ static int tcp_make (stio_dev_t* dev, void* ctx)
 	if (setsockopt (tcp->sck, SOL_SOCKET, SO_REUSEADDR, &iv, STIO_SIZEOF(iv)) == -1 ||
 	    bind (tcp->sck, (struct sockaddr*)&arg->addr, len) == -1) 
 	{
-		// TODO: set errnum from errno ...
-		//dev->stio->errnum = STIO_EINVAL;
+		tcp->stio->errnum = stio_syserrtoerrnum(errno);
 		goto oops;
 	}
 
@@ -124,6 +123,7 @@ static int tcp_recv (stio_dev_t* dev, void* buf, stio_len_t* len)
 	{
 		if (errno == EINPROGRESS || errno == EWOULDBLOCK) return 0;  /* no data available */
 		if (errno == EINTR) return 0;
+		tcp->stio->errnum = stio_syserrtoerrnum(errno);
 		return -1;
 	}
 
@@ -146,6 +146,7 @@ static int tcp_send (stio_dev_t* dev, const void* data, stio_len_t* len)
 	{
 		if (errno == EINPROGRESS || errno == EWOULDBLOCK) return 0;  /* no data can be written */
 		if (errno == EINTR) return 0;
+		tcp->stio->errnum = stio_syserrtoerrnum(errno);
 		return -1;
 	}
 
@@ -199,7 +200,7 @@ static int tcp_ioctl (stio_dev_t* dev, int cmd, void* arg)
 			x = bind (tcp->sck, sa, sl);
 			if (x == -1)
 			{
-				/* TODO: set dev->errnum from errno */
+				tcp->stio->errnum = stio_syserrtoerrnum(errno);
 				return -1;
 			}
 
@@ -264,7 +265,7 @@ static int tcp_ioctl (stio_dev_t* dev, int cmd, void* arg)
 					}
 				}
 
-				/* TODO: set dev->errnum from errno */
+				tcp->stio->errnum = stio_syserrtoerrnum(errno);
 				return -1;
 			}
 
@@ -288,7 +289,7 @@ static int tcp_ioctl (stio_dev_t* dev, int cmd, void* arg)
 			x = listen (tcp->sck, lstn->backlogs);
 			if (x == -1) 
 			{
-				/* TODO: set tcp->stio->errnum */
+				tcp->stio->errnum = stio_syserrtoerrnum(errno);
 				return -1;
 			}
 
@@ -340,9 +341,14 @@ printf ("TCP READY...%p\n", dev);
 			stio_scklen_t len;
 
 			len = STIO_SIZEOF(errcode);
-			if (getsockopt (tcp->sck, SOL_SOCKET, SO_ERROR, (char*)&errcode, &len) == 0)
+			if (getsockopt (tcp->sck, SOL_SOCKET, SO_ERROR, (char*)&errcode, &len) == -1)
 			{
-				printf ("CANNOT CONNECT ERRORCODE - %s\n", strerror(errcode));
+printf ("CANNOT CONNECT ERRORCODE - %s\n", strerror(errcode));
+				tcp->stio->errnum = stio_syserrtoerrnum(errno);
+			}
+			else
+			{
+				tcp->stio->errnum = stio_syserrtoerrnum(errcode);
 			}
 
 			return -1;
@@ -354,11 +360,11 @@ printf ("TCP READY...%p\n", dev);
 
 			STIO_ASSERT (!(tcp->state & STIO_DEV_TCP_CONNECTED));
 
-	printf ("XXXXXXXXXXXXXXX CONNECTED...\n");
+printf ("XXXXXXXXXXXXXXX CONNECTED...\n");
 			len = STIO_SIZEOF(errcode);
 			if (getsockopt (tcp->sck, SOL_SOCKET, SO_ERROR, (char*)&errcode, &len) == -1)
 			{
-				printf ("CANNOT GET SOCKET CONNECTION STATE....\n");
+				tcp->stio->errnum = stio_syserrtoerrnum(errno);
 				return -1;
 			}
 			else if (errcode == 0)
@@ -368,7 +374,7 @@ printf ("TCP READY...%p\n", dev);
 
 				if (stio_dev_event ((stio_dev_t*)tcp, STIO_DEV_EVENT_UPD, STIO_DEV_EVENT_IN) <= -1)
 				{
-					printf ("CAANOT MANIPULTE EVENT ...\n");
+printf ("CAANOT MANIPULTE EVENT ...\n");
 					return -1;
 				}
 
@@ -390,7 +396,7 @@ printf ("TCP READY...%p\n", dev);
 			}
 			else
 			{
-				printf ("failed to get SOCKET PROGRESS CODE...\n");
+				tcp->stio->errnum = stio_syserrtoerrnum(errcode);
 				return -1;
 			}
 		}
@@ -413,7 +419,7 @@ printf ("TCP READY...%p\n", dev);
 			if (errno == EINPROGRESS || errno == EWOULDBLOCK) return 0;
 			if (errno == EINTR) return 0; /* if interrupted by a signal, treat it as if it's EINPROGRESS */
 
-			/* TODO: set tcp->stio->errnum from errno */
+			tcp->stio->errnum = stio_syserrtoerrnum(errno);
 			return -1;
 		}
 
@@ -432,7 +438,6 @@ printf ("TCP READY...%p\n", dev);
 		clitcp->parent = tcp;
 
 
-
 		/* inherit some event handlers from the parent.
 		 * you can still change them inside the on_connected handler */
 		clitcp->on_connected = tcp->on_connected;
@@ -475,9 +480,9 @@ static stio_dev_evcb_t tcp_evcb =
 	tcp_on_sent
 };
 
-stio_dev_tcp_t* stio_dev_tcp_make (stio_t* stio, stio_size_t xtnsize, const stio_dev_tcp_make_t* arg)
+stio_dev_tcp_t* stio_dev_tcp_make (stio_t* stio, stio_size_t xtnsize, const stio_dev_tcp_make_t* data)
 {
-	return (stio_dev_tcp_t*)stio_makedev (stio, STIO_SIZEOF(stio_dev_tcp_t) + xtnsize, &tcp_mth, &tcp_evcb, (void*)arg);
+	return (stio_dev_tcp_t*)stio_makedev (stio, STIO_SIZEOF(stio_dev_tcp_t) + xtnsize, &tcp_mth, &tcp_evcb, (void*)data);
 }
 
 void stio_dev_tcp_kill (stio_dev_tcp_t* tcp)
diff --git a/stio/lib/stio-udp.c b/stio/lib/stio-udp.c
index 226b54c..096ebe3 100644
--- a/stio/lib/stio-udp.c
+++ b/stio/lib/stio-udp.c
@@ -36,36 +36,25 @@
 
 static int udp_make (stio_dev_t* dev, void* ctx)
 {
-/* NOTE: this can be extended to use ctx to tell between INET and INET6 or other types of sockets without creating a new dev method set. */
-
 	stio_dev_udp_t* udp = (stio_dev_udp_t*)dev;
-	struct sockaddr* saddr = (struct sockaddr*)ctx;
+	stio_dev_udp_make_t* arg = (stio_dev_udp_make_t*)ctx;
+	stio_scklen_t len;
+	stio_sckfam_t family;
 
-	udp->sck = stio_openasyncsck (AF_INET, SOCK_DGRAM);
+	if (stio_getsckadrinfo(dev->stio, &arg->addr, &len, &family) <= -1) return -1;
+
+	udp->sck = stio_openasyncsck (family, SOCK_DGRAM);
 	if (udp->sck == STIO_SCKHND_INVALID) goto oops;
 
-	if (saddr)
+	/* some socket options? */
+	if (bind (udp->sck, (struct sockaddr*)&arg->addr, len) == -1) 
 	{
-		stio_scklen_t len;
-		if (saddr->sa_family == AF_INET) 
-			len = STIO_SIZEOF(struct sockaddr_in);
-		else if (saddr->sa_family == AF_INET6)
-			len = STIO_SIZEOF(struct sockaddr_in6);
-		else	
-		{
-			dev->stio->errnum = STIO_EINVAL;
-			goto oops;
-		}
-
-
-		//setsockopt (udp->sck, SOL_SOCKET, SO_REUSEADDR, ...);
-		if (bind (udp->sck, saddr, len) == -1) 
-		{
-			//dev->stio->errnum = STIO_EINVAL; TODO:
-			goto oops;
-		}
+		udp->stio->errnum = stio_syserrtoerrnum(errno);
+		goto oops;
 	}
 
+	udp->on_sent = arg->on_sent;
+	udp->on_recv = arg->on_recv;
 	return 0;
 
 oops:
@@ -99,12 +88,15 @@ static int udp_recv (stio_dev_t* dev, void* buf, stio_len_t* len)
 	stio_scklen_t addrlen;
 	int x;
 
+/* TODO: udp_recv need source address ... have to extend the send callback to accept the source address */
 printf ("UDP RECVFROM...\n");
 	addrlen = STIO_SIZEOF(udp->peer);
 	x = recvfrom (udp->sck, buf, *len, 0, (struct sockaddr*)&udp->peer, &addrlen);
 	if (x <= -1)
 	{
 		if (errno == EINPROGRESS || errno == EWOULDBLOCK) return 0;  /* no data available */
+		if (errno == EINTR) return 0;
+		udp->stio->errnum = stio_syserrtoerrnum(errno);
 		return -1;
 	}
 
@@ -118,10 +110,13 @@ static int udp_send (stio_dev_t* dev, const void* data, stio_len_t* len)
 	ssize_t x;
 
 #if 0
+/* TODO: udp_send need target address ... have to extend the send callback to accept the target address */
 	x = sendto (udp->sck, data, *len, skad, stio_getskadlen(skad));
 	if (x <= -1) 
 	{
 		if (errno == EINPROGRESS || errno == EWOULDBLOCK) return 0;  /* no data can be written */
+		if (errno == EINTR) return 0;
+		udp->stio->errnum = stio_syserrtoerrnum(errno);
 		return -1;
 	}
 
@@ -157,6 +152,7 @@ static stio_dev_mth_t udp_mth =
 
 static int udp_ready (stio_dev_t* dev, int events)
 {
+/* TODO: ... */
 	if (events & STIO_DEV_EVENT_ERR) printf ("UDP READY ERROR.....\n");
 	if (events & STIO_DEV_EVENT_HUP) printf ("UDP READY HANGUP.....\n");
 	if (events & STIO_DEV_EVENT_PRI) printf ("UDP READY PRI.....\n");
@@ -187,13 +183,9 @@ static stio_dev_evcb_t udp_evcb =
 };
 
 
-stio_dev_udp_t* stio_dev_udp_make (stio_t* stio, stio_size_t xtnsize, stio_sckadr_t* addr)
+stio_dev_udp_t* stio_dev_udp_make (stio_t* stio, stio_size_t xtnsize, const stio_dev_udp_make_t* data)
 {
-	stio_dev_udp_t* udp;
-
-	udp = (stio_dev_udp_t*)stio_makedev (stio, STIO_SIZEOF(*udp) + xtnsize, &udp_mth, &udp_evcb, addr);
-
-	return udp;
+	return (stio_dev_udp_t*)stio_makedev (stio, STIO_SIZEOF(stio_dev_udp_t) + xtnsize, &udp_mth, &udp_evcb, (void*)data);
 }
 
 
diff --git a/stio/lib/stio-udp.h b/stio/lib/stio-udp.h
index 50dcbc6..29fa00f 100644
--- a/stio/lib/stio-udp.h
+++ b/stio/lib/stio-udp.h
@@ -32,13 +32,27 @@
 
 typedef struct stio_dev_udp_t stio_dev_udp_t;
 
+typedef int (*stio_dev_udp_on_recv_t) (stio_dev_udp_t* dev, const void* data, stio_len_t len);
+typedef int (*stio_dev_udp_on_sent_t) (stio_dev_udp_t* dev, void* sendctx);
+
+typedef struct stio_dev_udp_make_t stio_dev_udp_make_t;
+struct stio_dev_udp_make_t
+{
+	/* TODO: options: REUSEADDR for binding?? */
+	stio_sckadr_t addr; /* binding address. */
+	stio_dev_udp_on_sent_t on_sent;
+	stio_dev_udp_on_recv_t on_recv;
+};
+
 struct stio_dev_udp_t
 {
 	STIO_DEV_HEADERS;
 	stio_sckhnd_t sck;
 	stio_sckadr_t peer;
-};
 
+	stio_dev_udp_on_sent_t on_sent;
+	stio_dev_udp_on_recv_t on_recv;
+};
 
 #ifdef __cplusplus
 extern "C" {
@@ -46,9 +60,9 @@ extern "C" {
 
 
 STIO_EXPORT stio_dev_udp_t* stio_dev_udp_make (
-	stio_t*        stio,
-	stio_size_t    xtnsize,
-	stio_sckadr_t* addr
+	stio_t*                    stio,
+	stio_size_t                xtnsize,
+	const stio_dev_udp_make_t* data
 );
 
 STIO_EXPORT void stio_dev_udp_kill (
diff --git a/stio/lib/stio.c b/stio/lib/stio.c
index 3673a92..e77f4d9 100644
--- a/stio/lib/stio.c
+++ b/stio/lib/stio.c
@@ -32,9 +32,6 @@
 #include <unistd.h>
 #include <errno.h>
 
-
-
-
 stio_t* stio_open (stio_mmgr_t* mmgr, stio_size_t xtnsize, stio_size_t tmrcapa, stio_errnum_t* errnum)
 {
 	stio_t* stio;
@@ -73,8 +70,7 @@ int stio_init (stio_t* stio, stio_mmgr_t* mmgr, stio_size_t tmrcapa)
 	stio->mux = epoll_create (1000);
 	if (stio->mux == -1)
 	{
-/* TODO: set error number */
-		//if (stio->errnum) *errnum = XXXXX
+		stio->errnum = stio_syserrtoerrnum(errno);
 		return -1;
 	}
 
@@ -256,9 +252,8 @@ int stio_exec (stio_t* stio)
 	if (nentries <= -1)
 	{
 		if (errno == EINTR) return 0; /* it's actually ok */
-
 		/* other errors are critical - EBADF, EFAULT, EINVAL */
-		/* TODO: set errnum */
+		stio->errnum = stio_syserrtoerrnum(errno);
 		return -1;
 	}
 
@@ -508,7 +503,7 @@ int stio_dev_event (stio_dev_t* dev, stio_dev_event_cmd_t cmd, int flags)
 
 	if (epoll_ctl (dev->stio->mux, epoll_op, dev->mth->getsyshnd(dev), &ev) == -1)
 	{
-		/* TODO: set dev->stio->errnum from errno */
+		dev->stio->errnum = stio_syserrtoerrnum(errno);
 		return -1;
 	}
 
@@ -576,3 +571,30 @@ int stio_dev_send (stio_dev_t* dev, const void* data, stio_len_t len, void* send
 	dev->evcb->on_sent (dev, sendctx);
 	return 0;
 }
+
+
+stio_errnum_t stio_syserrtoerrnum (int no)
+{
+	switch (no)
+	{
+		case ENOMEM:
+			return STIO_ENOMEM;
+
+		case EINVAL:
+			return STIO_EINVAL;
+
+		case ENOENT:
+			return STIO_ENOENT;
+
+		case EMFILE:
+			return STIO_EMFILE;
+
+	#if defined(ENFILE)
+		case ENFILE:
+			return STIO_ENFILE;
+	#endif
+
+		default:
+			return STIO_ESYSERR;
+	}
+}
diff --git a/stio/lib/stio.h b/stio/lib/stio.h
index aa1f4a3..a2496bc 100644
--- a/stio/lib/stio.h
+++ b/stio/lib/stio.h
@@ -94,8 +94,11 @@ enum stio_errnum_t
 	STIO_EINVAL,
 	STIO_ENOENT,
 	STIO_ENOSUP, /* not supported */
+	STIO_EMFILE,
+	STIO_ENFILE,
 
-	STIO_EDEVMAKE
+	STIO_EDEVMAKE,
+	STIO_ESYSERR
 };
 
 typedef enum stio_errnum_t stio_errnum_t;