diff --git a/lib/http2.c b/lib/http2.c
index ab08b137..24d5ba41 100644
--- a/lib/http2.c
+++ b/lib/http2.c
@@ -74,6 +74,7 @@ lws_create_server_child_wsi(struct libwebsocket_context *context, struct libwebs
 	parent_wsi->u.http2.child_count++;
 	
 	wsi->u.http2.my_priority = 16;
+	wsi->u.http2.tx_credit = 65535;
 	
 	wsi->state = WSI_STATE_HTTP2_ESTABLISHED;
 	wsi->mode = parent_wsi->mode;
@@ -156,7 +157,13 @@ int lws_http2_frame_write(struct libwebsocket *wsi, int type, int flags, unsigne
 	*p++ = sid;
 	
 	lwsl_info("%s: %p (eff %p). type %d, flags 0x%x, sid=%d, len=%d\n",
-		  __func__, wsi, wsi_eff, type, flags, sid, len);
+		  __func__, wsi, wsi_eff, type, flags, sid, len, wsi->u.http2.tx_credit);
+	
+	if (type == LWS_HTTP2_FRAME_TYPE_DATA) {
+		if (wsi->u.http2.tx_credit < len)
+			lwsl_err("%s: %p: sending payload len %d but tx_credit only %d!\n", len, wsi->u.http2.tx_credit);
+		wsi->u.http2.tx_credit -= len;
+	}
 
 	n = lws_issue_raw(wsi_eff, &buf[-LWS_HTTP2_FRAME_HEADER_LENGTH], len + LWS_HTTP2_FRAME_HEADER_LENGTH);
 	if (n >= LWS_HTTP2_FRAME_HEADER_LENGTH)
@@ -195,6 +202,7 @@ lws_http2_parser(struct libwebsocket_context *context,
 			lwsl_info("http2: %p: established\n", wsi);
 			wsi->state = WSI_STATE_HTTP2_ESTABLISHED_PRE_SETTINGS;
 			wsi->u.http2.count = 0;
+			wsi->u.http2.tx_credit = 65535;
 			
 			/* 
 			 * we must send a settings frame -- empty one is OK...
@@ -255,6 +263,8 @@ lws_http2_parser(struct libwebsocket_context *context,
 				}
 				break;
 			case LWS_HTTP2_FRAME_TYPE_WINDOW_UPDATE:
+				wsi->u.http2.hpack_e_dep <<= 8;
+				wsi->u.http2.hpack_e_dep |= c;
 				break;
 			}
 			if (wsi->u.http2.count != wsi->u.http2.length)
@@ -264,6 +274,7 @@ lws_http2_parser(struct libwebsocket_context *context,
 
 			wsi->u.http2.frame_state = 0;
 			wsi->u.http2.count = 0;
+			swsi = wsi->u.http2.stream_wsi;
 			/* set our initial window size */
 			if (!wsi->u.http2.initialized) {
 				wsi->u.http2.tx_credit = wsi->u.http2.peer_settings.setting[LWS_HTTP2_SETTINGS__INITIAL_WINDOW_SIZE];
@@ -274,7 +285,7 @@ lws_http2_parser(struct libwebsocket_context *context,
 			case LWS_HTTP2_FRAME_TYPE_HEADERS:
 				/* service the http request itself */
 				lwsl_info("servicing initial http request, wsi=%p, stream wsi=%p\n", wsi, wsi->u.http2.stream_wsi);
-				n = lws_http_action(context, wsi->u.http2.stream_wsi);
+				n = lws_http_action(context, swsi);
 				lwsl_info("  action result %d\n", n);
 				break;
 			case LWS_HTTP2_FRAME_TYPE_PING:
@@ -283,6 +294,17 @@ lws_http2_parser(struct libwebsocket_context *context,
 					lws_set_protocol_write_pending(context, wsi, LWS_PPS_HTTP2_PONG);
 				}
 				break;
+			case LWS_HTTP2_FRAME_TYPE_WINDOW_UPDATE:
+				wsi->u.http2.hpack_e_dep &= ~(1 << 31);
+				if ((long long)swsi->u.http2.tx_credit + (unsigned long long)wsi->u.http2.hpack_e_dep > (~(1 << 31)))
+					return 1; /* actually need to close swsi not the whole show */
+				swsi->u.http2.tx_credit += wsi->u.http2.hpack_e_dep;
+				if (swsi->u.http2.waiting_tx_credit && swsi->u.http2.tx_credit > 0) {
+					lwsl_info("%s: %p: waiting_tx_credit -> wait on writeable\n", __func__, wsi);
+					swsi->u.http2.waiting_tx_credit = 0;
+					libwebsocket_callback_on_writable(context, swsi);
+				}	
+				break;
 			}
 			break;
 		}
@@ -307,7 +329,6 @@ lws_http2_parser(struct libwebsocket_context *context,
 		case 8:
 			wsi->u.http2.stream_id <<= 8;
 			wsi->u.http2.stream_id |= c;
-			wsi->u.http2.stream_wsi = wsi;
 			break;
 		}
 		if (wsi->u.http2.frame_state == LWS_HTTP2_FRAME_HEADER_LENGTH) { /* frame header complete */
@@ -315,6 +336,9 @@ lws_http2_parser(struct libwebsocket_context *context,
 				  wsi->u.http2.type, wsi->u.http2.flags, wsi->u.http2.stream_id, wsi->u.http2.length);
 			wsi->u.http2.count = 0;
 			
+			wsi->u.http2.stream_wsi = wsi;
+			if (wsi->u.http2.stream_id)
+				wsi->u.http2.stream_wsi = lws_http2_wsi_from_id(wsi, wsi->u.http2.stream_id);
 			
 			switch (wsi->u.http2.type) {
 			case LWS_HTTP2_FRAME_TYPE_SETTINGS:
@@ -342,7 +366,6 @@ lws_http2_parser(struct libwebsocket_context *context,
 				lwsl_info("LWS_HTTP2_FRAME_TYPE_HEADERS: stream_id = %d\n", wsi->u.http2.stream_id);
 				if (!wsi->u.http2.stream_id)
 					return 1;
-				wsi->u.http2.stream_wsi = lws_http2_wsi_from_id(wsi, wsi->u.http2.stream_id);
 				if (!wsi->u.http2.stream_wsi)
 					wsi->u.http2.stream_wsi = lws_create_server_child_wsi(context, wsi, wsi->u.http2.stream_id);
 								
@@ -374,6 +397,10 @@ update_end_headers:
 						swsi->u.http2.hpack = HPKS_TYPE;
 				lwsl_info("initial hpack state %d\n", swsi->u.http2.hpack);
 				break;
+			case LWS_HTTP2_FRAME_TYPE_WINDOW_UPDATE:
+				if (wsi->u.http2.length != 4)
+					return 1;
+				break;
 			}
 			if (wsi->u.http2.length == 0)
 				wsi->u.http2.frame_state = 0;
@@ -391,6 +418,8 @@ int lws_http2_do_pps_send(struct libwebsocket_context *context, struct libwebsoc
 	struct libwebsocket *swsi;
 	int n, m = 0;
 
+	lwsl_debug("%s: %p: %d\n", __func__, wsi, wsi->pps);
+	
 	switch (wsi->pps) {
 	case LWS_PPS_HTTP2_MY_SETTINGS:
 		for (n = 1; n < LWS_HTTP2_SETTINGS__COUNT; n++)
diff --git a/lib/libwebsockets.c b/lib/libwebsockets.c
index 5b365165..5cf78eba 100644
--- a/lib/libwebsockets.c
+++ b/lib/libwebsockets.c
@@ -821,7 +821,7 @@ void lws_set_protocol_write_pending(struct libwebsocket_context *context,
 				    struct libwebsocket *wsi,
 				    enum lws_pending_protocol_send pend)
 {
-		lwsl_err("setting pps %d\n", pend);
+	lwsl_info("setting pps %d\n", pend);
 	
 	if (wsi->pps)
 		lwsl_err("pps overwrite\n");
@@ -829,3 +829,20 @@ void lws_set_protocol_write_pending(struct libwebsocket_context *context,
 	libwebsocket_rx_flow_control(wsi, 0);
 	libwebsocket_callback_on_writable(context, wsi);
 }
+
+LWS_VISIBLE size_t
+lws_get_peer_write_allowance(struct libwebsocket *wsi)
+{
+#ifdef LWS_USE_HTTP2
+	/* only if we are using HTTP2 on this connection */
+	if (wsi->mode != LWS_CONNMODE_HTTP2_SERVING)
+		return -1;
+	/* user is only interested in how much he can send, or that he can't  */
+	if (wsi->u.http2.tx_credit <= 0)
+		return 0;
+	
+	return wsi->u.http2.tx_credit;
+#else
+	return -1;
+#endif
+}
diff --git a/lib/libwebsockets.h b/lib/libwebsockets.h
index 0ed5592d..ca382ce4 100644
--- a/lib/libwebsockets.h
+++ b/lib/libwebsockets.h
@@ -153,9 +153,11 @@ LWS_VISIBLE LWS_EXTERN void lwsl_hexdump(void *buf, size_t len);
 
 #define LWS_FEATURE_SERVE_HTTP_FILE_HAS_OTHER_HEADERS_ARG
 
-    /* the struct libwebsocket_protocols has the id field present */
+/* the struct libwebsocket_protocols has the id field present */
 #define LWS_FEATURE_PROTOCOLS_HAS_ID_FIELD
 
+/* you can call lws_get_peer_write_allowance */
+#define LWS_FEATURE_PROTOCOLS_HAS_PEER_WRITE_ALLOWANCE
 
 enum libwebsocket_context_options {
 	LWS_SERVER_OPTION_REQUIRE_VALID_OPENSSL_CLIENT_CERT = 2,
@@ -1226,6 +1228,25 @@ libwebsocket_rx_flow_allow_all_protocol(
 LWS_VISIBLE LWS_EXTERN size_t
 libwebsockets_remaining_packet_payload(struct libwebsocket *wsi);
 
+/*
+ * if the protocol does not have any guidence, returns -1.  Currently only
+ * http2 connections get send window information from this API.  But your code
+ * should use it so it can work properly with any protocol.
+ * 
+ * If nonzero return is the amount of payload data the peer or intermediary has
+ * reported it has buffer space for.  That has NO relationship with the amount
+ * of buffer space your OS can accept on this connection for a write action.
+ * 
+ * This number represents the maximum you could send to the peer or intermediary
+ * on this connection right now without it complaining.
+ * 
+ * lws manages accounting for send window updates and payload writes
+ * automatically, so this number reflects the situation at the peer or
+ * intermediary dynamically.
+ */
+LWS_VISIBLE LWS_EXTERN size_t
+lws_get_peer_write_allowance(struct libwebsocket *wsi);
+
 LWS_VISIBLE LWS_EXTERN struct libwebsocket *
 libwebsocket_client_connect(struct libwebsocket_context *clients,
 			      const char *address,
diff --git a/lib/pollfd.c b/lib/pollfd.c
index 63cdfc36..10fd8108 100644
--- a/lib/pollfd.c
+++ b/lib/pollfd.c
@@ -207,6 +207,19 @@ libwebsocket_callback_on_writable(struct libwebsocket_context *context,
 		return 1;
 	}
 	
+	if (wsi->u.http2.tx_credit <= 0) {
+		/*
+		 * other side is not able to cope with us sending
+		 * anything so no matter if we have POLLOUT on our side.
+		 * 
+		 * Delay waiting for our POLLOUT until peer indicates he has
+		 * space for more using tx window command in http2 layer
+		 */
+		lwsl_info("%s: %p: waiting_tx_credit (%d)\n", __func__, wsi, wsi->u.http2.tx_credit);
+		wsi->u.http2.waiting_tx_credit = 1;
+		return 0;
+	}
+	
 	network_wsi = lws_http2_get_network_wsi(wsi);
 	already = network_wsi->u.http2.requested_POLLOUT;
 	
diff --git a/lib/private-libwebsockets.h b/lib/private-libwebsockets.h
index ac7e7c3e..da9c7a1c 100755
--- a/lib/private-libwebsockets.h
+++ b/lib/private-libwebsockets.h
@@ -708,6 +708,7 @@ struct _lws_http2_related {
 	unsigned int send_END_STREAM:1;
 	unsigned int GOING_AWAY;
 	unsigned int requested_POLLOUT:1;
+	unsigned int waiting_tx_credit:1;
 
 	/* hpack */
 	enum http2_hpack_state hpack;
@@ -720,7 +721,8 @@ struct _lws_http2_related {
 	unsigned int huff:1;
 	unsigned int value:1;
 	
-	unsigned int tx_credit;
+	/* negative credit is mandated by the spec */
+	int tx_credit;
 	unsigned int my_stream_id;
 	unsigned int child_count;
 	int my_priority;
diff --git a/lib/server.c b/lib/server.c
index 1c6afd24..3e7e471b 100644
--- a/lib/server.c
+++ b/lib/server.c
@@ -426,9 +426,9 @@ upgrade_h2c:
 		       "HTTP/1.1 101 Switching Protocols\x0d\x0a"
 		      "Connection: Upgrade\x0d\x0a"
 		      "Upgrade: h2c\x0d\x0a\x0d\x0a");
-		n = lws_issue_raw(wsi, (unsigned char *)wsi->protocol->name,
-					strlen(wsi->protocol->name));
-		if (n != strlen(wsi->protocol->name)) {
+		n = lws_issue_raw(wsi, (unsigned char *)protocol_list,
+					strlen(protocol_list));
+		if (n != strlen(protocol_list)) {
 			lwsl_debug("http2 switch: ERROR writing to socket\n");
 			return 1;
 		}
diff --git a/lib/ssl-http2.c b/lib/ssl-http2.c
index 134231f2..832d9150 100644
--- a/lib/ssl-http2.c
+++ b/lib/ssl-http2.c
@@ -140,8 +140,6 @@ void lws_http2_configure_if_upgraded(struct libwebsocket *wsi)
 
 	ah = wsi->u.hdr.ah;
 
-	wsi->mode = LWS_CONNMODE_HTTP2_SERVING;
-
 	/* union transition */
 	memset(&wsi->u, 0, sizeof(wsi->u));