Add AsyncSend example

Author: mathieucarbou

examples/AsyncSend/AsyncSend.ino

@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// Copyright 2016-2025 Hristo Gochkov, Mathieu Carbou, Emil Muratov
+
+/*
+  This example demonstrates how to send data to a remote server asynchronously.
+  Run on the remote computer: nc -l -p 1234
+
+  You should see in the logs:
+
+Connected!
+Will send 5760 bytes...
+Acked 1436 bytes in 19 ms
+Will send 1436 bytes...
+Acked 1436 bytes in 2 ms
+Will send 996 bytes...
+Waiting for acks...
+Acked 1436 bytes in 1 ms
+Acked 1436 bytes in 5 ms
+Acked 1452 bytes in 17 ms
+Acked 996 bytes in 28 ms
+Buffer received - next send in 2 sec
+Will send 5760 bytes...
+Acked 1436 bytes in 14 ms
+Will send 1436 bytes...
+Acked 1436 bytes in 2 ms
+Acked 1436 bytes in 0 ms
+Acked 1452 bytes in 1 ms
+Will send 996 bytes...
+Waiting for acks...
+Acked 1436 bytes in 3 ms
+Acked 996 bytes in 18 ms
+Buffer received - next send in 2 sec
+
+  And in the remote terminal 3072 characters sent [.........  ...........] and so on.
+*/
+
+#include <Arduino.h>
+#include <AsyncTCP.h>
+#include <StreamString.h>
+#include <WiFi.h>
+
+#include <functional>
+#include <string>
+
+#define WIFI_SSID     "IoT"
+#define WIFI_PASSWORD ""
+
+#define REMOTE_IP   "192.168.125.116"
+#define REMOTE_PORT 1234
+
+#define BUFFER_SIZE 8 * 1024
+
+static char buffer[BUFFER_SIZE] = {0};
+static size_t bufferPos = 0;
+
+// 0 == disconnected
+// 1 == connecting
+// 2 == connected
+static uint8_t state = 0;
+
+// number of bytes waiting for a ack
+static size_t waitingAck = 0;
+
+static AsyncClient client;
+
+void setup() {
+  Serial.begin(115200);
+  while (!Serial) {
+    continue;
+  }
+
+  // connect to WiFi
+  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
+  while (WiFi.status() != WL_CONNECTED) {
+    delay(500);
+  }
+  Serial.println("Connected to WiFi!");
+  Serial.println(WiFi.localIP());
+
+  // fill buffer
+  buffer[0] = '[';
+  for (size_t i = 1; i < BUFFER_SIZE - 1; i++) {
+    buffer[i] = '.';
+  }
+  buffer[BUFFER_SIZE - 1] = ']';
+
+  // register a callback when the client disconnects
+  client.onDisconnect([](void *arg, AsyncClient *client) {
+    Serial.printf("Disconnected.\n");
+    state = 0;
+  });
+
+  // register a callback when an error occurs
+  client.onError([](void *arg, AsyncClient *client, int8_t error) {
+    Serial.printf("Error: %s\n", client->errorToString(error));
+  });
+
+  // register a callback when data arrives, to accumulate it
+  client.onData([](void *arg, AsyncClient *client, void *data, size_t len) {
+    Serial.printf("Received %u bytes...\n", len);
+    Serial.write((uint8_t *)data, len);
+  });
+
+  // register a callback when we are connected
+  client.onConnect([](void *arg, AsyncClient *client) {
+    Serial.printf("Connected!\n");
+    state = 2;
+  });
+
+  client.onAck([](void *arg, AsyncClient *client, size_t len, uint32_t time) {
+    Serial.printf("Acked %u bytes in %" PRIu32 " ms\n", len, time);
+    assert(waitingAck >= len);
+    waitingAck -= len;
+  });
+
+  client.setRxTimeout(20000);
+  client.setNoDelay(true);
+}
+
+void loop() {
+  switch (state) {
+    case 0:
+    {
+      Serial.printf("Connecting...\n");
+      if (!client.connect(REMOTE_IP, REMOTE_PORT)) {
+        Serial.printf("Failed to connect!\n");
+        delay(1000);  // to not flood logs
+      } else {
+        state = 1;
+      }
+      break;
+    }
+
+    case 1:
+    {
+      Serial.printf("Still connecting...\n");
+      delay(500);  // to not flood logs
+      break;
+    }
+
+    case 2:
+    {
+      // fill PCB space until we can
+      size_t willSend;
+      while (bufferPos < BUFFER_SIZE && (willSend = client.write(buffer + bufferPos, BUFFER_SIZE - bufferPos))) {
+        Serial.printf("Will send %u bytes...\n", willSend);
+        bufferPos += willSend;
+        waitingAck += willSend;
+      }
+
+      // we have sent the whole buffer ?
+      if (bufferPos >= BUFFER_SIZE) {
+        // wait for acks, or send again after 2 sec
+        if (waitingAck) {
+          Serial.printf("Waiting for acks...\n");
+          delay(100);
+        } else {
+          Serial.printf("Buffer received - next send in 2 sec\n");
+          delay(2000);
+          bufferPos = 0;
+        }
+      }
+      break;
+    }
+
+    default: break;
+  }
+}

platformio.ini

@@ -2,7 +2,8 @@
 default_envs = arduino-2, arduino-3
 lib_dir = .
 ; src_dir = examples/Client
-src_dir = examples/FetchWebsite
+; src_dir = examples/FetchWebsite
+src_dir = examples/AsyncSend
 
 [env]
 framework = arduino