From 6fc96b977f5b4b110cb174fff3327ef9245ee0d6 Mon Sep 17 00:00:00 2001
From: me-no-dev <hristo@espressif.com>
Date: Thu, 2 Mar 2017 02:49:53 +0200
Subject: [PATCH] Add WiFiClient flush to clear all non-read data in RX

fixes: https://github.com/espressif/arduino-esp32/issues/119
---
 libraries/WiFi/src/WiFiClient.cpp | 27 +++++++++++++++++++++++++++
 libraries/WiFi/src/WiFiClient.h   |  2 +-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/libraries/WiFi/src/WiFiClient.cpp b/libraries/WiFi/src/WiFiClient.cpp
index 20041bdc..a8f81b32 100644
--- a/libraries/WiFi/src/WiFiClient.cpp
+++ b/libraries/WiFi/src/WiFiClient.cpp
@@ -24,6 +24,7 @@
 
 #define WIFI_CLIENT_MAX_WRITE_RETRY   (10)
 #define WIFI_CLIENT_SELECT_TIMEOUT_US (100000)
+#define WIFI_CLIENT_FLUSH_BUFFER_SIZE (1024)
 
 #undef connect
 #undef write
@@ -251,6 +252,32 @@ int WiFiClient::available()
     return count;
 }
 
+// Though flushing means to send all pending data,
+// seems that in Arduino it also means to clear RX
+void WiFiClient::flush() {
+    size_t a = available(), toRead = 0;
+    if(!a){
+        return;//nothing to flush
+    }
+    uint8_t * buf = (uint8_t *)malloc(WIFI_CLIENT_FLUSH_BUFFER_SIZE);
+    if(!buf){
+        return;//memory error
+    }
+    while(a){
+        toRead = (a>WIFI_CLIENT_FLUSH_BUFFER_SIZE)?WIFI_CLIENT_FLUSH_BUFFER_SIZE:a;
+        if(recv(fd(), buf, toRead, MSG_DONTWAIT) < 0) {
+            if(errno != EWOULDBLOCK){
+                log_e("%d", errno);
+                stop();
+                break;
+            }
+            delay(1);//give some time
+        }
+        a = available();
+    }
+    free(buf);
+}
+
 uint8_t WiFiClient::connected()
 {
     uint8_t dummy = 0;
diff --git a/libraries/WiFi/src/WiFiClient.h b/libraries/WiFi/src/WiFiClient.h
index 02df4319..36f66e16 100644
--- a/libraries/WiFi/src/WiFiClient.h
+++ b/libraries/WiFi/src/WiFiClient.h
@@ -49,7 +49,7 @@ public:
     {
         return 0;
     }
-    void flush() {}
+    void flush();
     void stop();
     uint8_t connected();