diff --git a/moo/kernel/Socket.moo b/moo/kernel/Socket.moo
index 29c7a7e..ba4db53 100644
--- a/moo/kernel/Socket.moo
+++ b/moo/kernel/Socket.moo
@@ -234,6 +234,7 @@ class Socket(Object) from 'sck'
 	var inwc := 0, outwc := 0. ## input watcher count and ouput watcher count
 	var insem, outsem.
 	var(#get,#set) inputAction, outputAction.
+	var(#get) inputReady := false, outputReady := false.
 
 	method(#primitive) open(domain, type, proto).
 	method(#primitive) _close.
@@ -339,9 +340,20 @@ extend Socket
 	{
 		| old_output_action |
 
+		if (self.outputReady)
+		{
+			if ((self _writeBytes: bytes) >= 0) { ^self }.
+			self.outputReady := false.
+		}.
+
 		old_output_action := self.outputAction.
 		self.outputAction := [ :sck :state |
-			self _writeBytes: bytes.
+			if ((self _writeBytes: bytes) <= -1) 
+			{
+				## EAGAIN
+				self.outputReady := false.
+				^self.
+			}.
 ## TODO: handle _writeBytes may not write in full.
 
 			## restore the output action block before executing the previous
@@ -364,9 +376,13 @@ extend Socket
 			if (self.insem isNil)
 			{
 				self.insem := Semaphore new.
-				self.insem signalAction: [:sem | self.inputAction value: self value: true].
+				self.insem signalAction: [:sem | 
+					self.inputReady := true.
+					self.inputAction value: self value: true
+				].
 				System addAsyncSemaphore: self.insem.
 			}.
+			self.inputReady := false.
 			System signal: self.insem onInput: self.handle 
 		}.
 		self.inwc := self.inwc + 1.
@@ -392,9 +408,13 @@ extend Socket
 			if (self.outsem isNil)
 			{
 				self.outsem := Semaphore new.
-				self.outsem signalAction: [:sem | self.outputAction value: self value: true].
+				self.outsem signalAction: [:sem | 
+					self.outputReady := true.
+					self.outputAction value: self value: true 
+				].
 				System addAsyncSemaphore: self.outsem.
 			}.
+			self.outputReady := false.
 			System signal: self.outsem onOutput: self.handle.
 		}.
 		self.outwc := self.outwc + 1.
diff --git a/moo/lib/main.c b/moo/lib/main.c
index 038a1a2..fbbfef5 100644
--- a/moo/lib/main.c
+++ b/moo/lib/main.c
@@ -859,7 +859,7 @@ static int _add_poll_fd (moo_t* moo, int fd, int event_mask)
 	/* epoll_wait may return again if the worker thread consumes events.
 	 * switch to level-trigger. */
 	/* TODO: verify if EPOLLLET is desired */
-	//ev.events |= EPOLLET;
+	ev.events |= EPOLLET;
 	#endif
 	/*ev.data.ptr = (void*)event_data;*/
 	ev.data.fd = fd;
@@ -1043,7 +1043,7 @@ static int _mod_poll_fd (moo_t* moo, int fd, int event_mask)
 	/* epoll_wait may return again if the worker thread consumes events.
 	 * switch to level-trigger. */
 	/* TODO: verify if EPOLLLET is desired */
-	//ev.events |= EPOLLET;
+	ev.events |= EPOLLET;
 	#endif
 	ev.data.fd = fd;
 	if (epoll_ctl (xtn->ep, EPOLL_CTL_MOD, fd, &ev) == -1)
@@ -1357,7 +1357,7 @@ static int vm_muxadd (moo_t* moo, moo_ooi_t io_handle, moo_ooi_t mask)
 {
 	int event_mask;
 
-	event_mask = 0; /*EPOLLET; */ /* TODO: use edge trigger(EPOLLLET)? */
+	event_mask = 0;
 	if (mask & MOO_SEMAPHORE_IO_MASK_INPUT) event_mask |= XPOLLIN; 
 	if (mask & MOO_SEMAPHORE_IO_MASK_OUTPUT) event_mask |= XPOLLOUT;
 
@@ -1368,14 +1368,14 @@ static int vm_muxadd (moo_t* moo, moo_ooi_t io_handle, moo_ooi_t mask)
 		return -1;
 	}
 
-	return _add_poll_fd (moo, io_handle, event_mask);
+	return _add_poll_fd(moo, io_handle, event_mask);
 }
 
 static int vm_muxmod (moo_t* moo, moo_ooi_t io_handle, moo_ooi_t mask)
 {
 	int event_mask;
 
-	event_mask = 0; /*EPOLLET; */ /* TODO: use edge trigger(EPOLLLET)? */
+	event_mask = 0;
 	if (mask & MOO_SEMAPHORE_IO_MASK_INPUT) event_mask |= XPOLLIN; 
 	if (mask & MOO_SEMAPHORE_IO_MASK_OUTPUT) event_mask |= XPOLLOUT;
 
@@ -1386,12 +1386,12 @@ static int vm_muxmod (moo_t* moo, moo_ooi_t io_handle, moo_ooi_t mask)
 		return -1;
 	}
 
-	return _mod_poll_fd (moo, io_handle, event_mask);
+	return _mod_poll_fd(moo, io_handle, event_mask);
 }
 
 static int vm_muxdel (moo_t* moo, moo_ooi_t io_handle)
 {
-	return _del_poll_fd (moo, io_handle);
+	return _del_poll_fd(moo, io_handle);
 }
 
 #if defined(USE_THREAD)
diff --git a/moo/mod/sck.c b/moo/mod/sck.c
index 132221b..9df0284 100644
--- a/moo/mod/sck.c
+++ b/moo/mod/sck.c
@@ -396,13 +396,15 @@ static moo_pfrc_t pf_read_socket (moo_t* moo, moo_ooi_t nargs)
 		return MOO_PF_FAILURE;
 	}
 
-	n = recv (fd, MOO_OBJ_GET_BYTE_SLOT(buf), MOO_OBJ_GET_SIZE(buf), 0);
-	if (n <= -1 && errno != EWOULDBLOCK)
+	n = recv(fd, MOO_OBJ_GET_BYTE_SLOT(buf), MOO_OBJ_GET_SIZE(buf), 0);
+	if (n <= -1 && errno != EWOULDBLOCK && errno != EAGAIN)
 	{
 		moo_seterrwithsyserr (moo, errno);
 		return MOO_PF_FAILURE;
 	}
 
+	/* NOTE: on EWOULDBLOCK or EGAIN, -1 is returned  */
+
 	MOO_ASSERT (moo, MOO_IN_SMOOI_RANGE(n));
 
 	MOO_STACK_SETRET (moo, nargs, MOO_SMOOI_TO_OOP(n));
@@ -438,7 +440,6 @@ static moo_pfrc_t pf_write_socket (moo_t* moo, moo_ooi_t nargs)
 		return MOO_PF_FAILURE;
 	}
 
-
 	offset = 0;
 	maxlen = MOO_OBJ_GET_SIZE(buf);
 	length = maxlen;
@@ -457,7 +458,7 @@ static moo_pfrc_t pf_write_socket (moo_t* moo, moo_ooi_t nargs)
 		if (nargs >= 3)
 		{
 			tmp = MOO_STACK_GETARG(moo, nargs, 2);
-			if (moo_inttooow (moo, tmp, &length) <= 0)
+			if (moo_inttooow(moo, tmp, &length) <= 0)
 			{
 				moo_seterrbfmt (moo, MOO_EINVAL, "invalid length - %O", tmp);
 				return MOO_PF_FAILURE;
@@ -468,13 +469,14 @@ static moo_pfrc_t pf_write_socket (moo_t* moo, moo_ooi_t nargs)
 		if (length > maxlen - offset) length = maxlen - offset;
 	}
 
-	n = send (fd, &MOO_OBJ_GET_BYTE_SLOT(buf)[offset], length, 0);
-	if (n <= -1 && errno != EWOULDBLOCK)
+	n = send(fd, &MOO_OBJ_GET_BYTE_SLOT(buf)[offset], length, 0);
+	if (n <= -1 && errno != EWOULDBLOCK && errno != EAGAIN)
 	{
 		moo_seterrwithsyserr (moo, errno);
 		return MOO_PF_FAILURE;
 	}
 
+	/* NOTE: on EWOULDBLOCK or EGAIN, -1 is returned  */
 	MOO_ASSERT (moo, MOO_IN_SMOOI_RANGE(n));
 
 	MOO_STACK_SETRET (moo, nargs, MOO_SMOOI_TO_OOP(n));