diff --git a/src/pkg/net/fd.go b/src/pkg/net/fd.go
index 607a6c1..596cf33 100644
--- a/src/pkg/net/fd.go
+++ b/src/pkg/net/fd.go
@@ -7,6 +7,7 @@
 package net
 
 import (
+	"errors"
 	"io"
 	"os"
 	"sync"
@@ -19,6 +20,9 @@
 	// locking/lifetime of sysfd
 	sysmu   sync.Mutex
 	sysref  int
+	
+	// must lock both sysmu and pollserver to write
+	// can lock either to read
 	closing bool
 
 	// immutable until Close
@@ -27,8 +31,8 @@
 	sotype      int
 	isConnected bool
 	sysfile     *os.File
-	cr          chan bool
-	cw          chan bool
+	cr          chan error
+	cw          chan error
 	net         string
 	laddr       Addr
 	raddr       Addr
@@ -86,19 +90,14 @@
 	deadline   int64 // next deadline (nsec since 1970)
 }
 
-func (s *pollServer) AddFD(fd *netFD, mode int) {
-	intfd := fd.sysfd
-	if intfd < 0 {
-		// fd closed underfoot
-		if mode == 'r' {
-			fd.cr <- true
-		} else {
-			fd.cw <- true
-		}
-		return
-	}
-
+func (s *pollServer) AddFD(fd *netFD, mode int) error {
 	s.Lock()
+	intfd := fd.sysfd
+	if intfd < 0 || fd.closing {
+		// fd closed underfoot
+		s.Unlock()
+		return errClosing
+	}
 
 	var t int64
 	key := intfd << 1
@@ -124,12 +123,28 @@
 	if wake {
 		doWakeup = true
 	}
-
 	s.Unlock()
 
 	if doWakeup {
 		s.Wakeup()
 	}
+	return nil
+}
+
+// Evict evicts fd from the pending list, unblocking
+// any I/O running on fd.  The caller must have locked
+// pollserver.
+func (s *pollServer) Evict(fd *netFD) {
+	if s.pending[fd.sysfd<<1] == fd {
+		s.WakeFD(fd, 'r', errClosing)
+		s.poll.DelFD(fd.sysfd, 'r')
+		delete(s.pending, fd.sysfd<<1)
+	}
+	if s.pending[fd.sysfd<<1|1] == fd {
+		s.WakeFD(fd, 'w', errClosing)
+		s.poll.DelFD(fd.sysfd, 'w')
+		delete(s.pending, fd.sysfd<<1|1)
+	}
 }
 
 var wakeupbuf [1]byte
@@ -149,16 +164,16 @@
 	return netfd
 }
 
-func (s *pollServer) WakeFD(fd *netFD, mode int) {
+func (s *pollServer) WakeFD(fd *netFD, mode int, err error) {
 	if mode == 'r' {
 		for fd.ncr > 0 {
 			fd.ncr--
-			fd.cr <- true
+			fd.cr <- err
 		}
 	} else {
 		for fd.ncw > 0 {
 			fd.ncw--
-			fd.cw <- true
+			fd.cw <- err
 		}
 	}
 }
@@ -196,7 +211,7 @@
 					s.poll.DelFD(fd.sysfd, mode)
 					fd.wdeadline = -1
 				}
-				s.WakeFD(fd, mode)
+				s.WakeFD(fd, mode, nil)
 			} else if next_deadline == 0 || t < next_deadline {
 				next_deadline = t
 			}
@@ -240,19 +255,25 @@
 				print("pollServer: unexpected wakeup for fd=", fd, " mode=", string(mode), "\n")
 				continue
 			}
-			s.WakeFD(netfd, mode)
+			s.WakeFD(netfd, mode, nil)
 		}
 	}
 }
 
-func (s *pollServer) WaitRead(fd *netFD) {
-	s.AddFD(fd, 'r')
-	<-fd.cr
+func (s *pollServer) WaitRead(fd *netFD) error {
+	err := s.AddFD(fd, 'r')
+	if err == nil {
+		err = <-fd.cr
+	}
+	return err
 }
 
-func (s *pollServer) WaitWrite(fd *netFD) {
-	s.AddFD(fd, 'w')
-	<-fd.cw
+func (s *pollServer) WaitWrite(fd *netFD) error {
+	err := s.AddFD(fd, 'w')
+	if err == nil {
+		err = <-fd.cw
+	}
+	return err
 }
 
 // Network FD methods.
@@ -280,8 +301,8 @@
 		sotype: sotype,
 		net:    net,
 	}
-	netfd.cr = make(chan bool, 1)
-	netfd.cw = make(chan bool, 1)
+	netfd.cr = make(chan error, 1)
+	netfd.cw = make(chan error, 1)
 	return netfd, nil
 }
 
@@ -301,7 +322,9 @@
 func (fd *netFD) connect(ra syscall.Sockaddr) error {
 	err := syscall.Connect(fd.sysfd, ra)
 	if err == syscall.EINPROGRESS {
-		pollserver.WaitWrite(fd)
+		if err = pollserver.WaitWrite(fd); err != nil {
+			return err
+		}
 		var e int
 		e, err = syscall.GetsockoptInt(fd.sysfd, syscall.SOL_SOCKET, syscall.SO_ERROR)
 		if err != nil {
@@ -314,24 +337,37 @@
 	return err
 }
 
+var errClosing = errors.New("use of closed network connection")
+
 // Add a reference to this fd.
-func (fd *netFD) incref() {
+// If closing==true, pollserver must be locked; mark the fd as closing.
+// Returns an error if the fd cannot be used.
+func (fd *netFD) incref(closing bool) error {
+	if fd == nil {
+		return errClosing
+	}
 	fd.sysmu.Lock()
+	if fd.closing {
+		fd.sysmu.Unlock()
+		return errClosing
+	}
 	fd.sysref++
+	if closing {
+		fd.closing = true
+	}
 	fd.sysmu.Unlock()
+	return nil
 }
 
 // Remove a reference to this FD and close if we've been asked to do so (and
 // there are no references left.
 func (fd *netFD) decref() {
+	if fd == nil {
+		return
+	}
 	fd.sysmu.Lock()
 	fd.sysref--
-	if fd.closing && fd.sysref == 0 && fd.sysfd >= 0 {
-		// In case the user has set linger, switch to blocking mode so
-		// the close blocks.  As long as this doesn't happen often, we
-		// can handle the extra OS processes.  Otherwise we'll need to
-		// use the pollserver for Close too.  Sigh.
-		syscall.SetNonblock(fd.sysfd, false)
+	if fd.closing && fd.sysref == 0 && fd.sysfile != nil {
 		fd.sysfile.Close()
 		fd.sysfile = nil
 		fd.sysfd = -1
@@ -340,21 +376,26 @@
 }
 
 func (fd *netFD) Close() error {
-	if fd == nil || fd.sysfile == nil {
-		return os.EINVAL
+	pollserver.Lock()  // needed for both fd.incref(true) and pollserver.Evict
+	defer pollserver.Unlock()
+	if err := fd.incref(true); err != nil {
+		return err
 	}
-
-	fd.incref()
-	syscall.Shutdown(fd.sysfd, syscall.SHUT_RDWR)
-	fd.closing = true
+	// Unblock any I/O.  Once it all unblocks and returns,
+	// so that it cannot be referring to fd.sysfd anymore,
+	// the final decref will close fd.sysfd.  This should happen
+	// fairly quickly, since all the I/O is non-blocking, and any
+	// attempts to block in the pollserver will return errClosing.
+	pollserver.Evict(fd)
 	fd.decref()
 	return nil
 }
 
 func (fd *netFD) shutdown(how int) error {
-	if fd == nil || fd.sysfile == nil {
-		return os.EINVAL
+	if err := fd.incref(false); err != nil {
+		return err
 	}
+	defer fd.decref()
 	err := syscall.Shutdown(fd.sysfd, how)
 	if err != nil {
 		return &OpError{"shutdown", fd.net, fd.laddr, err}
@@ -371,24 +412,21 @@
 }
 
 func (fd *netFD) Read(p []byte) (n int, err error) {
-	if fd == nil {
-		return 0, os.EINVAL
-	}
 	fd.rio.Lock()
 	defer fd.rio.Unlock()
-	fd.incref()
-	defer fd.decref()
-	if fd.sysfile == nil {
-		return 0, os.EINVAL
+	if err := fd.incref(false); err != nil {
+		return 0, err
 	}
+	defer fd.decref()
 	for {
-		n, err = syscall.Read(int(fd.sysfile.Fd()), p)
+		n, err = syscall.Read(int(fd.sysfd), p)
 		if err == syscall.EAGAIN {
-			if fd.rdeadline >= 0 {
-				pollserver.WaitRead(fd)
-				continue
-			}
 			err = errTimeout
+			if fd.rdeadline >= 0 {
+				if err = pollserver.WaitRead(fd); err == nil {
+					continue
+				}
+			}
 		}
 		if err != nil {
 			n = 0
@@ -404,49 +442,49 @@
 }
 
 func (fd *netFD) ReadFrom(p []byte) (n int, sa syscall.Sockaddr, err error) {
-	if fd == nil || fd.sysfile == nil {
-		return 0, nil, os.EINVAL
-	}
 	fd.rio.Lock()
 	defer fd.rio.Unlock()
-	fd.incref()
+	if err := fd.incref(false); err != nil {
+		return 0, nil, err
+	}
 	defer fd.decref()
 	for {
 		n, sa, err = syscall.Recvfrom(fd.sysfd, p, 0)
 		if err == syscall.EAGAIN {
-			if fd.rdeadline >= 0 {
-				pollserver.WaitRead(fd)
-				continue
-			}
 			err = errTimeout
+			if fd.rdeadline >= 0 {
+				if err = pollserver.WaitRead(fd); err == nil {
+					continue
+				}
+			}
 		}
 		if err != nil {
 			n = 0
 		}
 		break
 	}
-	if err != nil {
+	if err != nil && err != io.EOF {
 		err = &OpError{"read", fd.net, fd.laddr, err}
 	}
 	return
 }
 
 func (fd *netFD) ReadMsg(p []byte, oob []byte) (n, oobn, flags int, sa syscall.Sockaddr, err error) {
-	if fd == nil || fd.sysfile == nil {
-		return 0, 0, 0, nil, os.EINVAL
-	}
 	fd.rio.Lock()
 	defer fd.rio.Unlock()
-	fd.incref()
+	if err := fd.incref(false); err != nil {
+		return 0, 0, 0, nil, err
+	}
 	defer fd.decref()
 	for {
 		n, oobn, flags, sa, err = syscall.Recvmsg(fd.sysfd, p, oob, 0)
 		if err == syscall.EAGAIN {
-			if fd.rdeadline >= 0 {
-				pollserver.WaitRead(fd)
-				continue
-			}
 			err = errTimeout
+			if fd.rdeadline >= 0 {
+				if err = pollserver.WaitRead(fd); err == nil {
+					continue
+				}
+			}
 		}
 		if err == nil && n == 0 {
 			err = io.EOF
@@ -461,12 +499,11 @@
 }
 
 func (fd *netFD) Write(p []byte) (int, error) {
-	if fd == nil {
-		return 0, os.EINVAL
-	}
 	fd.wio.Lock()
 	defer fd.wio.Unlock()
-	fd.incref()
+	if err := fd.incref(false); err != nil {
+		return 0, err
+	}
 	defer fd.decref()
 	if fd.sysfile == nil {
 		return 0, os.EINVAL
@@ -476,7 +513,7 @@
 	nn := 0
 	for {
 		var n int
-		n, err = syscall.Write(int(fd.sysfile.Fd()), p[nn:])
+		n, err = syscall.Write(int(fd.sysfd), p[nn:])
 		if n > 0 {
 			nn += n
 		}
@@ -484,11 +521,12 @@
 			break
 		}
 		if err == syscall.EAGAIN {
-			if fd.wdeadline >= 0 {
-				pollserver.WaitWrite(fd)
-				continue
-			}
 			err = errTimeout
+			if fd.wdeadline >= 0 {
+				if err = pollserver.WaitWrite(fd); err == nil {
+					continue
+				}
+			}
 		}
 		if err != nil {
 			n = 0
@@ -506,21 +544,21 @@
 }
 
 func (fd *netFD) WriteTo(p []byte, sa syscall.Sockaddr) (n int, err error) {
-	if fd == nil || fd.sysfile == nil {
-		return 0, os.EINVAL
-	}
 	fd.wio.Lock()
 	defer fd.wio.Unlock()
-	fd.incref()
+	if err := fd.incref(false); err != nil {
+		return 0, err
+	}
 	defer fd.decref()
 	for {
 		err = syscall.Sendto(fd.sysfd, p, 0, sa)
 		if err == syscall.EAGAIN {
-			if fd.wdeadline >= 0 {
-				pollserver.WaitWrite(fd)
-				continue
-			}
 			err = errTimeout
+			if fd.wdeadline >= 0 {
+				if err = pollserver.WaitWrite(fd); err == nil {
+					continue
+				}
+			}
 		}
 		break
 	}
@@ -533,21 +571,21 @@
 }
 
 func (fd *netFD) WriteMsg(p []byte, oob []byte, sa syscall.Sockaddr) (n int, oobn int, err error) {
-	if fd == nil || fd.sysfile == nil {
-		return 0, 0, os.EINVAL
-	}
 	fd.wio.Lock()
 	defer fd.wio.Unlock()
-	fd.incref()
+	if err := fd.incref(false); err != nil {
+		return 0, 0, err
+	}
 	defer fd.decref()
 	for {
 		err = syscall.Sendmsg(fd.sysfd, p, oob, sa, 0)
 		if err == syscall.EAGAIN {
-			if fd.wdeadline >= 0 {
-				pollserver.WaitWrite(fd)
-				continue
-			}
 			err = errTimeout
+			if fd.wdeadline >= 0 {
+				if err = pollserver.WaitWrite(fd); err == nil {
+					continue
+				}
+			}
 		}
 		break
 	}
@@ -561,11 +599,9 @@
 }
 
 func (fd *netFD) accept(toAddr func(syscall.Sockaddr) Addr) (netfd *netFD, err error) {
-	if fd == nil || fd.sysfile == nil {
-		return nil, os.EINVAL
+	if err := fd.incref(false); err != nil {
+		return nil, err
 	}
-
-	fd.incref()
 	defer fd.decref()
 
 	// See ../syscall/exec.go for description of ForkLock.
@@ -574,19 +610,17 @@
 	var s int
 	var rsa syscall.Sockaddr
 	for {
-		if fd.closing {
-			return nil, os.EINVAL
-		}
 		syscall.ForkLock.RLock()
 		s, rsa, err = syscall.Accept(fd.sysfd)
 		if err != nil {
 			syscall.ForkLock.RUnlock()
 			if err == syscall.EAGAIN {
-				if fd.rdeadline >= 0 {
-					pollserver.WaitRead(fd)
-					continue
-				}
 				err = errTimeout
+				if fd.rdeadline >= 0 {
+					if err = pollserver.WaitRead(fd); err == nil {
+						continue
+					}
+				}
 			}
 			return nil, &OpError{"accept", fd.net, fd.laddr, err}
 		}