Implement WiFiClient.peek()

Thanks @miomir1981

libraries/WiFi/src/WiFiClient.cpp

@@ -237,6 +237,20 @@ int WiFiClient::read(uint8_t *buf, size_t size)
     return res;
 }
 
+int WiFiClient::peek()
+{
+    if(!available()) {
+        return -1;
+    }
+    uint8_t data = 0;
+    int res = recv(fd(), &data, 1, MSG_PEEK);
+    if(res < 0 && errno != EWOULDBLOCK) {
+        log_e("%d", errno);
+        stop();
+    }
+    return data;
+}
+
 int WiFiClient::available()
 {
     if(!_connected) {

libraries/WiFi/src/WiFiClient.h

@@ -47,10 +47,7 @@ public:
     int available();
     int read();
     int read(uint8_t *buf, size_t size);
-    int peek()
-    {
-        return -1;
-    }
+    int peek();
     void flush();
     void stop();
     uint8_t connected();