diff --git a/conn.go b/conn.go
index d704e18..302dd31 100644
--- a/conn.go
+++ b/conn.go
@@ -2,12 +2,13 @@ package stomp
 
 import (
 	"errors"
-	"gopkg.in/stomp.v1/frame"
 	"io"
 	"log"
 	"net"
 	"strconv"
 	"time"
+
+	"gopkg.in/stomp.v1/frame"
 )
 
 // Default time span to add to read/write heart-beat timeouts
@@ -59,6 +60,7 @@ type Conn struct {
 	server       string
 	readTimeout  time.Duration
 	writeTimeout time.Duration
+	closed       bool
 }
 
 type writeRequest struct {
@@ -299,12 +301,15 @@ func processLoop(c *Conn, writer *Writer) {
 				}
 
 			case frame.ERROR:
-				log.Println("received ERROR")
+				log.Println("received ERROR; Closing underlying connection")
 				for _, ch := range channels {
 					ch <- f
 					close(ch)
 				}
 
+				c.closed = true
+				c.conn.Close()
+
 				return
 
 			case frame.MESSAGE:
@@ -372,6 +377,10 @@ func sendError(m map[string]chan *Frame, err error) {
 // with the STOMP server is closed and any further attempt to write
 // to the server will fail.
 func (c *Conn) Disconnect() error {
+	if c.closed {
+		return nil
+	}
+
 	ch := make(chan *Frame)
 	c.writeCh <- writeRequest{
 		Frame: NewFrame(frame.DISCONNECT, frame.Receipt, allocateId()),
@@ -383,6 +392,7 @@ func (c *Conn) Disconnect() error {
 		return newError(response)
 	}
 
+	c.closed = true
 	return c.conn.Close()
 }
 
@@ -397,7 +407,10 @@ func (c *Conn) Disconnect() error {
 // The message can contain optional, user-defined header entries in userDefined. If there are no optional header
 // entries, then set userDefined to nil.
 func (c *Conn) Send(destination, contentType string, body []byte, userDefined *Header) error {
-	// TODO(jpj): Check that we are still connected before sending.
+	if c.closed {
+		return newErrorMessage("Underlying connection closed.")
+	}
+
 	f := createSendFrame(destination, contentType, body, userDefined)
 	f.Del(frame.Transaction)
 	c.sendFrame(f)
@@ -414,7 +427,10 @@ func (c *Conn) Send(destination, contentType string, body []byte, userDefined *H
 // The message can contain optional, user-defined header entries in userDefined. If there are no optional header
 // entries, then set userDefined to nil.
 func (c *Conn) SendWithReceipt(destination, contentType string, body []byte, userDefined *Header) error {
-	// TODO(jpj): Check that we are still connected before sending.
+	if c.closed {
+		return newErrorMessage("Underlying connection closed.")
+	}
+
 	f := createSendFrame(destination, contentType, body, userDefined)
 	f.Del(frame.Transaction)
 	return c.sendFrameWithReceipt(f)