diff --git a/examples/basic.c b/examples/basic.c
index fb9299d..bd0ab22 100644
--- a/examples/basic.c
+++ b/examples/basic.c
@@ -38,7 +38,25 @@ void conn_handler(xmpp_conn_t *const conn,
                 secured ? "secured" : "NOT secured");
         xmpp_disconnect(conn);
     } else {
-        fprintf(stderr, "DEBUG: disconnected\n");
+        switch (error) {
+        case XMPP_EOK:
+            fprintf(stderr, "DEBUG: disconnected successfully.\n");
+            break;
+        case XMPP_EINVOP:
+            /*
+             * This may happen when the requested functionality is not
+             * supported or some data is not provided when it is required (e.g.
+             * resource part).
+             */
+            fprintf(stderr, "DEBUG: disconnected, invalid operation.\n");
+            break;
+        case XMPP_ECERT:
+            /*
+             * In this case, application can reconnect with
+             * XMPP_CONN_FLAG_TRUST_TLS if user permits.
+             */
+            fprintf(stderr, "DEBUG: disconnected, invalid TLS certificate.\n");
+        }
         xmpp_stop(ctx);
     }
 }
diff --git a/src/auth.c b/src/auth.c
index 31732ae..fa8441d 100644
--- a/src/auth.c
+++ b/src/auth.c
@@ -349,7 +349,7 @@ static int _handle_sasl_result(xmpp_conn_t *const conn,
                    "Got unexpected reply to SASL %s"
                    "authentication.",
                    (char *)userdata);
-        xmpp_disconnect(conn);
+        disconnect_with_error(conn, XMPP_EINT);
     }
 
     return 0;
@@ -644,7 +644,7 @@ static void _auth(xmpp_conn_t *const conn)
         xmpp_error(conn->ctx, "xmpp",
                    "TLS is not supported, but set as "
                    "mandatory for this connection");
-        conn_disconnect(conn);
+        disconnect_with_error(conn, XMPP_EINVOP);
         return;
     }
 
@@ -667,7 +667,7 @@ static void _auth(xmpp_conn_t *const conn)
     } else if (anonjid) {
         xmpp_error(conn->ctx, "auth",
                    "No node in JID, and SASL ANONYMOUS unsupported.");
-        xmpp_disconnect(conn);
+        disconnect_with_error(conn, XMPP_EINVOP);
     } else if (conn->sasl_support & SASL_MASK_SCRAM) {
         scram_ctx = xmpp_alloc(conn->ctx, sizeof(*scram_ctx));
         if (conn->sasl_support & SASL_MASK_SCRAMSHA512)
@@ -780,7 +780,7 @@ static void _auth(xmpp_conn_t *const conn)
         _auth_legacy(conn);
     } else {
         xmpp_error(conn->ctx, "auth", "Cannot authenticate with known methods");
-        xmpp_disconnect(conn);
+        disconnect_with_error(conn, XMPP_EAUTH);
     }
 }
 
@@ -930,7 +930,7 @@ static int _handle_features_sasl(xmpp_conn_t *const conn,
         xmpp_error(conn->ctx, "xmpp",
                    "Stream features does not allow "
                    "resource bind.");
-        xmpp_disconnect(conn);
+        disconnect_with_error(conn, XMPP_EINT);
     }
 
     return 0;
@@ -944,7 +944,7 @@ static int _handle_missing_features_sasl(xmpp_conn_t *const conn,
     xmpp_error(conn->ctx, "xmpp",
                "Did not receive stream features "
                "after SASL authentication.");
-    xmpp_disconnect(conn);
+    disconnect_with_error(conn, XMPP_ETIMEDOUT);
     return 0;
 }
 
@@ -964,7 +964,7 @@ static int _handle_bind(xmpp_conn_t *const conn,
     type = xmpp_stanza_get_type(stanza);
     if (type && strcmp(type, "error") == 0) {
         xmpp_error(conn->ctx, "xmpp", "Binding failed.");
-        xmpp_disconnect(conn);
+        disconnect_with_error(conn, XMPP_EINT);
     } else if (type && strcmp(type, "result") == 0) {
         xmpp_stanza_t *binding = xmpp_stanza_get_child_by_name(stanza, "bind");
         xmpp_debug(conn->ctx, "xmpp", "Bind successful.");
@@ -1016,7 +1016,7 @@ static int _handle_bind(xmpp_conn_t *const conn,
         }
     } else {
         xmpp_error(conn->ctx, "xmpp", "Server sent malformed bind reply.");
-        xmpp_disconnect(conn);
+        disconnect_with_error(conn, XMPP_EINT);
     }
 
     return 0;
@@ -1027,7 +1027,7 @@ static int _handle_missing_bind(xmpp_conn_t *const conn, void *const userdata)
     UNUSED(userdata);
 
     xmpp_error(conn->ctx, "xmpp", "Server did not reply to bind request.");
-    xmpp_disconnect(conn);
+    disconnect_with_error(conn, XMPP_ETIMEDOUT);
     return 0;
 }
 
@@ -1046,7 +1046,7 @@ static int _handle_session(xmpp_conn_t *const conn,
     type = xmpp_stanza_get_type(stanza);
     if (type && strcmp(type, "error") == 0) {
         xmpp_error(conn->ctx, "xmpp", "Session establishment failed.");
-        xmpp_disconnect(conn);
+        disconnect_with_error(conn, XMPP_EINT);
     } else if (type && strcmp(type, "result") == 0) {
         xmpp_debug(conn->ctx, "xmpp", "Session establishment successful.");
 
@@ -1056,7 +1056,7 @@ static int _handle_session(xmpp_conn_t *const conn,
         conn->conn_handler(conn, XMPP_CONN_CONNECT, 0, NULL, conn->userdata);
     } else {
         xmpp_error(conn->ctx, "xmpp", "Server sent malformed session reply.");
-        xmpp_disconnect(conn);
+        disconnect_with_error(conn, XMPP_EINT);
     }
 
     return 0;
@@ -1068,7 +1068,7 @@ static int _handle_missing_session(xmpp_conn_t *const conn,
     UNUSED(userdata);
 
     xmpp_error(conn->ctx, "xmpp", "Server did not reply to session request.");
-    xmpp_disconnect(conn);
+    disconnect_with_error(conn, XMPP_ETIMEDOUT);
     return 0;
 }
 
@@ -1079,7 +1079,7 @@ static int _handle_missing_legacy(xmpp_conn_t *const conn, void *const userdata)
     xmpp_error(conn->ctx, "xmpp",
                "Server did not reply to legacy "
                "authentication request.");
-    xmpp_disconnect(conn);
+    disconnect_with_error(conn, XMPP_ETIMEDOUT);
     return 0;
 }
 
@@ -1102,11 +1102,11 @@ static int _handle_legacy(xmpp_conn_t *const conn,
         xmpp_error(conn->ctx, "xmpp",
                    "Server sent us an unexpected response "
                    "to legacy authentication request.");
-        xmpp_disconnect(conn);
+        disconnect_with_error(conn, XMPP_EINT);
     } else if (strcmp(type, "error") == 0) {
         /* legacy client auth failed, no more fallbacks */
         xmpp_error(conn->ctx, "xmpp", "Legacy client authentication failed.");
-        xmpp_disconnect(conn);
+        disconnect_with_error(conn, XMPP_EAUTH);
     } else if (strcmp(type, "result") == 0) {
         /* auth succeeded */
         xmpp_debug(conn->ctx, "xmpp", "Legacy auth succeeded.");
@@ -1117,7 +1117,7 @@ static int _handle_legacy(xmpp_conn_t *const conn,
         xmpp_error(conn->ctx, "xmpp",
                    "Server sent us a legacy authentication "
                    "response with a bad type.");
-        xmpp_disconnect(conn);
+        disconnect_with_error(conn, XMPP_EINT);
     }
 
     return 0;
@@ -1197,7 +1197,7 @@ static void _auth_legacy(xmpp_conn_t *conn)
         xmpp_stanza_release(authdata);
         xmpp_stanza_release(iq);
         xmpp_error(conn->ctx, "auth", "Cannot authenticate without resource");
-        xmpp_disconnect(conn);
+        disconnect_with_error(conn, XMPP_EINVOP);
         return;
     }
     xmpp_stanza_add_child(child, authdata);
@@ -1231,7 +1231,7 @@ void auth_handle_component_open(xmpp_conn_t *const conn)
     rc = _handle_component_auth(conn);
     if (rc != 0) {
         xmpp_error(conn->ctx, "auth", "Component authentication failed.");
-        xmpp_disconnect(conn);
+        disconnect_with_error(conn, rc);
     }
 }
 
@@ -1298,15 +1298,8 @@ int _handle_component_hs_response(xmpp_conn_t *const conn,
 
     name = xmpp_stanza_get_name(stanza);
     if (strcmp(name, "handshake") != 0) {
-        char *msg;
-        size_t msg_size;
-        xmpp_stanza_to_text(stanza, &msg, &msg_size);
-        if (msg) {
-            xmpp_debug(conn->ctx, "auth", "Handshake failed: %s", msg);
-            xmpp_free(conn->ctx, msg);
-        }
-        xmpp_disconnect(conn);
-        return XMPP_EINT;
+        xmpp_debug(conn->ctx, "auth", "Handshake failed.");
+        disconnect_with_error(conn, XMPP_EINT);
     } else {
         conn->authenticated = 1;
         conn->conn_handler(conn, XMPP_CONN_CONNECT, 0, NULL, conn->userdata);
@@ -1323,7 +1316,7 @@ int _handle_missing_handshake(xmpp_conn_t *const conn, void *const userdata)
     UNUSED(userdata);
 
     xmpp_error(conn->ctx, "xmpp", "Server did not reply to handshake request.");
-    xmpp_disconnect(conn);
+    disconnect_with_error(conn, XMPP_ETIMEDOUT);
     return 0;
 }
 
diff --git a/src/common.h b/src/common.h
index ddc30fd..2070b78 100644
--- a/src/common.h
+++ b/src/common.h
@@ -276,6 +276,7 @@ void handler_add(xmpp_conn_t *const conn,
 void handler_system_delete_all(xmpp_conn_t *conn);
 
 /* utility functions */
+void disconnect_with_error(xmpp_conn_t *const conn, int error);
 void disconnect_mem_error(xmpp_conn_t *const conn);
 
 /* auth functions */
diff --git a/src/conn.c b/src/conn.c
index 9c145bf..f7dfb7d 100644
--- a/src/conn.c
+++ b/src/conn.c
@@ -918,8 +918,8 @@ int conn_tls_start(xmpp_conn_t *const conn)
         if (tls_start(conn->tls)) {
             conn->secured = 1;
         } else {
-            rc = XMPP_EINT;
-            conn->error = tls_error(conn->tls);
+            /* TODO: distinguish invalid certificates and other errors */
+            rc = XMPP_ECERT;
             tls_free(conn->tls);
             conn->tls = NULL;
             conn->tls_failed = 1;
@@ -927,9 +927,9 @@ int conn_tls_start(xmpp_conn_t *const conn)
     }
     if (rc != 0) {
         xmpp_debug(conn->ctx, "conn",
-                   "Couldn't start TLS! "
-                   "error %d tls_error %d",
-                   rc, conn->error);
+                   "Couldn't start TLS! error %d tls_error %d", rc,
+                   conn->tls == NULL ? 0 : tls_error(conn->tls));
+        conn->error = rc;
     }
     return rc;
 }
@@ -1069,6 +1069,7 @@ static int _disconnect_cleanup(xmpp_conn_t *const conn, void *const userdata)
 
     xmpp_debug(conn->ctx, "xmpp", "disconnection forced by cleanup timeout");
 
+    conn->error = conn->error ?: XMPP_ETIMEDOUT;
     conn_disconnect(conn);
 
     return 0;
@@ -1195,7 +1196,7 @@ static void _handle_stream_start(char *name, char **attrs, void *const userdata)
 {
     xmpp_conn_t *conn = (xmpp_conn_t *)userdata;
     char *id;
-    int failed = 0;
+    int ret = 0;
 
     if (conn->stream_id)
         xmpp_free(conn->ctx, conn->stream_id);
@@ -1209,20 +1210,21 @@ static void _handle_stream_start(char *name, char **attrs, void *const userdata)
 
         if (id && !conn->stream_id) {
             xmpp_error(conn->ctx, "conn", "Memory allocation failed.");
-            failed = 1;
+            ret = XMPP_EMEM;
         }
     } else {
         xmpp_error(conn->ctx, "conn",
                    "Server did not open valid stream."
                    " name = %s.",
                    name);
-        failed = 1;
+        ret = XMPP_EINT;
     }
 
-    if (!failed) {
+    if (ret == 0) {
         /* call stream open handler */
         conn->open_handler(conn);
     } else {
+        conn->error = ret;
         conn_disconnect(conn);
     }
 }
diff --git a/src/event.c b/src/event.c
index b13845b..3be5c49 100644
--- a/src/event.c
+++ b/src/event.c
@@ -41,15 +41,6 @@
 #define _sleep(x) usleep((x)*1000)
 #else
 #include <winsock2.h>
-#ifndef ETIMEDOUT
-#define ETIMEDOUT WSAETIMEDOUT
-#endif
-#ifndef ECONNRESET
-#define ECONNRESET WSAECONNRESET
-#endif
-#ifndef ECONNABORTED
-#define ECONNABORTED WSAECONNABORTED
-#endif
 #define _sleep(x) Sleep(x)
 #endif
 
@@ -107,25 +98,23 @@ void xmpp_run_once(xmpp_ctx_t *ctx, const unsigned long timeout)
 
             if (ret < 0 && !tls_is_recoverable(tls_error(conn->tls))) {
                 /* an error occurred */
-                xmpp_debug(ctx, "xmpp", "Send error occurred, disconnecting.");
-                conn->error = ECONNABORTED;
-                conn_disconnect(conn);
+                conn->error = XMPP_EIO;
             }
         }
 
         /* write all data from the send queue to the socket */
         sq = conn->send_queue_head;
-        while (sq) {
+        while (!conn->error && sq) {
             towrite = sq->len - sq->written;
 
             if (conn->tls) {
                 ret = tls_write(conn->tls, &sq->data[sq->written], towrite);
                 if (ret < 0 && !tls_is_recoverable(tls_error(conn->tls)))
-                    conn->error = tls_error(conn->tls);
+                    conn->error = XMPP_EIO;
             } else {
                 ret = sock_write(conn->sock, &sq->data[sq->written], towrite);
                 if (ret < 0 && !sock_is_recoverable(sock_error()))
-                    conn->error = sock_error();
+                    conn->error = XMPP_EIO;
             }
             if (ret > 0 && ret < towrite)
                 sq->written += ret; /* not all data could be sent now */
@@ -151,7 +140,6 @@ void xmpp_run_once(xmpp_ctx_t *ctx, const unsigned long timeout)
             /* FIXME: need to tear down send queues and random other things
              * maybe this should be abstracted */
             xmpp_debug(ctx, "xmpp", "Send error occurred, disconnecting.");
-            conn->error = ECONNABORTED;
             conn_disconnect(conn);
         }
 
@@ -190,8 +178,8 @@ void xmpp_run_once(xmpp_ctx_t *ctx, const unsigned long timeout)
                 conn->connect_timeout)
                 FD_SET(conn->sock, &wfds);
             else {
-                conn->error = ETIMEDOUT;
                 xmpp_info(ctx, "xmpp", "Connection attempt timed out.");
+                conn->error = XMPP_ETIMEDOUT;
                 conn_disconnect(conn);
             }
             break;
@@ -252,6 +240,7 @@ void xmpp_run_once(xmpp_ctx_t *ctx, const unsigned long timeout)
                 if (ret != 0) {
                     /* connection failed */
                     xmpp_debug(ctx, "xmpp", "connection failed, error %d", ret);
+                    conn->error = XMPP_EIO;
                     conn_disconnect(conn);
                     break;
                 }
@@ -285,14 +274,14 @@ void xmpp_run_once(xmpp_ctx_t *ctx, const unsigned long timeout)
                             xmpp_debug(ctx, "xmpp",
                                        "Unrecoverable TLS error, %d.",
                                        tls_error(conn->tls));
-                            conn->error = tls_error(conn->tls);
+                            conn->error = XMPP_EIO;
                             conn_disconnect(conn);
                         }
                     } else {
                         /* return of 0 means socket closed by server */
                         xmpp_debug(ctx, "xmpp",
                                    "Socket closed by remote host.");
-                        conn->error = ECONNRESET;
+                        conn->error = ret == 0 ? XMPP_ERESET : XMPP_EIO;
                         conn_disconnect(conn);
                     }
                 }
diff --git a/src/util.c b/src/util.c
index 66f44aa..c085041 100644
--- a/src/util.c
+++ b/src/util.c
@@ -128,6 +128,20 @@ uint64_t time_elapsed(uint64_t t1, uint64_t t2)
     return (uint64_t)(t2 - t1);
 }
 
+/** Disconnect the stream with the error.
+ *  This is a convenience function used internally by various parts of
+ *  the Strophe library for terminating the connection because of an error.
+ *
+ *  @param conn a Strophe connection object
+ *  @param error an error code
+ */
+void disconnect_with_error(xmpp_conn_t *const conn, int error)
+{
+    xmpp_error(conn->ctx, "xmpp", "Disconnecting with error %d", error);
+    conn->error = conn->error ?: error;
+    xmpp_disconnect(conn);
+}
+
 /** Disconnect the stream with a memory error.
  *  This is a convenience function used internally by various parts of
  *  the Strophe library for terminating the connection because of a
@@ -138,5 +152,5 @@ uint64_t time_elapsed(uint64_t t1, uint64_t t2)
 void disconnect_mem_error(xmpp_conn_t *const conn)
 {
     xmpp_error(conn->ctx, "xmpp", "Memory allocation error");
-    xmpp_disconnect(conn);
+    disconnect_with_error(conn, XMPP_EMEM);
 }
diff --git a/strophe.h b/strophe.h
index daa244a..7e2c5dc 100644
--- a/strophe.h
+++ b/strophe.h
@@ -103,6 +103,26 @@ extern "C" {
  *  Internal failure error code.
  */
 #define XMPP_EINT -3
+/** @def XMPP_ECERT
+ *  Certificate verification failed during TLS establishment.
+ */
+#define XMPP_ECERT -4
+/** @def XMPP_ETIMEDOUT
+ *  Operation timed out error code.
+ */
+#define XMPP_ETIMEDOUT -5
+/** @def XMPP_EIO
+ *  I/O error code.
+ */
+#define XMPP_EIO -6
+/** @def XMPP_ERESET
+ *  Error code for situation when connection closed by remote side.
+ */
+#define XMPP_ERESET -7
+/** @def XMPP_EAUTH
+ *  Authentication failed error code.
+ */
+#define XMPP_EAUTH -8
 
 /* initialization and shutdown */
 void xmpp_initialize(void);