From 63694392ea096f5c421cb65cd2a8bb9146c5d872 Mon Sep 17 00:00:00 2001
From: David Gauchard <gauchard@laas.fr>
Date: Wed, 31 Jan 2018 11:26:21 +0100
Subject: [PATCH] ClientContext:_write_some: release buffer once data really
 accepted for sending may fix #1872

---
 libraries/ESP8266WiFi/src/include/ClientContext.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libraries/ESP8266WiFi/src/include/ClientContext.h b/libraries/ESP8266WiFi/src/include/ClientContext.h
index 43e9040a48..d53b453942 100644
--- a/libraries/ESP8266WiFi/src/include/ClientContext.h
+++ b/libraries/ESP8266WiFi/src/include/ClientContext.h
@@ -447,11 +447,13 @@ class ClientContext
             }
             err_t err = tcp_write(_pcb, buf, next_chunk, TCP_WRITE_FLAG_COPY);
             DEBUGV(":wrc %d %d %d\r\n", next_chunk, will_send, (int) err);
-            _datasource->release_buffer(buf, next_chunk);
             if (err == ERR_OK) {
+                _datasource->release_buffer(buf, next_chunk);
                 _written += next_chunk;
                 need_output = true;
             } else {
+		// ERR_MEM(-1) is a valid error meaning
+		// "come back later". It leaves state() opened
                 break;
             }
             will_send -= next_chunk;