从 Java 服务器向 ESP8266 发送数据

Question

这是我第一次 post 在这里，如果我有任何错误，请多多包涵...

好的，所以我只是想在我的计算机上安装一个 Java 程序运行ning 将信息发送到 ESP8266 运行ning arduino 软件。首先，这是代码。

ESP8266（Arduino）：

#include <ESP8266WiFi.h>

#define NAME "********"
#define PASS "********"

const char* host = "192.168.1.6";

WiFiClient client;

void setup() {
  Serial.begin(115200);
  Serial.println();
  WiFi.begin(NAME, PASS);
  Serial.print("Connecting");
  while(WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println();
  Serial.print("Connected, IP address: ");
  Serial.println(WiFi.localIP());

  if (client.connect(host, 9090)) {
    Serial.print("Connected to: ");
    Serial.println(host);
    String data = "No Message";
    client.print("ESP8266 connected!");
    if(client.available()) {
      data = client.readStringUntil('\n');
    }
    Serial.print("Host message: ");
    Serial.println(data);
    client.stop();
  } else {
    client.stop();
  }
}

void loop() {
}

Java 服务器：

import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {

    public static void main(String[] args) throws IOException {

        ServerSocket listener = new ServerSocket(9090);
        try{
            while(true){
                Socket socket = listener.accept();
                socket.setKeepAlive(true);
                try{
                    BufferedWriter out = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
                    out.write("Hello from Java!\n");
                } finally {
                    socket.close();
                }
            }
        } finally {
            listener.close();
        }
    }

}

问题是 client.available() 永远不会 returns 为真，即使 Java 服务器向客户端发送信息也是如此。我试过将数据从 Arduino 发送到服务器，效果很好。我还制作了一个快速 Java 程序，它可以运行作为客户端，并运行在网络上的另一台计算机上运行。本例中的 Java 服务器和客户端通信正常。所以问题出在 Arduino 的某个地方，但我不知道它是什么。

Answer 1

您的那部分代码属于 loop() 事件：

  if (client.connect(host, 9090)) {
    Serial.print("Connected to: ");
    Serial.println(host);
    String data = "No Message";
    client.print("ESP8266 connected!");
    if(client.available()) {
      data = client.readStringUntil('\n');
    }
    Serial.print("Host message: ");
    Serial.println(data);
    client.stop();
  } else {
    client.stop();
  }

setup() 函数仅运行一次。在它移动到 loop() 并停留在那里之后。而你的 loop() 函数是空的...

Answer 2

我遇到了同样的问题，这是我的解决方案：
Java 仅在添加 out.flush() 时更新输出流；在 out.write();

之后

还有

client.available()

返回 0 直到你读到一些东西。例如

String first_line = client.readStringUntil('\n');

之后你可以使用 available() 方法。

使用字符串 "Hello,\nthis is a text\n":

进行测试

client.println(client.available()); // 0

String first_line = client.readStringUntil('\n');

client.println(first_line); // Hello,
client.println(client.available()); // 17

要将所有消息发送回客户端：

client.print("First: ");
client.println(first_line);

while(client.available() > 0) {
  client.println("Next: " + client.readStringUntil('\n'));
}

输出：

First: Hello,
Next: this is a text
Next:

Answer 3

这里的问题似乎与

有关

client.print()

将其替换为

client.println()

解决了我的问题。

我相信这在某种程度上拖延了输入缓冲服务器端，因为它正在等待换行但从未得到换行。我将 post 更新后的代码，适用于任何有此问题的人。

ESP8266:

#include <ESP8266WiFi.h>

#define NAME "********"
#define PASS "********"

const char* host = "10.0.0.15";

WiFiClient client;

void setup() {
  Serial.begin(115200);
  Serial.println();

  /* Set Client up as station */
  WiFi.mode(WIFI_STA);

  WiFi.begin(NAME, PASS);

  /* Connect to the network */
  Serial.print("Connecting");
  while(WiFi.status() != WL_CONNECTED)
  {
    delay(500);
    Serial.print(".");
  }
  Serial.println();

  Serial.print("Connected, IP address: ");
  Serial.println(WiFi.localIP());
}

void loop() {
  if (client.connect(host, 9090))
  {
    Serial.print("Connected to: ");
    Serial.println(host);

    /* Send "connected" to the server so it knows we are ready for data */
    client.println("deviceconnected"); //USE client.println()!!
    Serial.println("Host message: \n");

    /* Wait for data for 5 seconds at most before timing out */
    unsigned long timeout = millis();
    while(client.available() == 0)
    {
      if(millis() - timeout > 5000)
      {
        Serial.println("Timeout to server!");
        break;
      }
    }

    /* Read in the data in the stream */
    while(client.available() > 0)
    {
      Serial.println(client.readStringUntil('\n'));
    }
    client.stop();
  }
  else
  {
    client.stop();
  }
  delay(5000);
}

Java 服务器：

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {

    public static void main(String[] args) throws IOException {

        ServerSocket listener = new ServerSocket(9090);
        try{
            while(true){
                Socket socket = listener.accept();
                socket.setKeepAlive(true);
                System.out.println("Client Connected");
                try{
                    BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                    System.out.println("Client response: " + in.readLine());

                    BufferedWriter out = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
                    System.out.println("Sending Message...");
                    out.write("Hello\n from Java!\n");
                    out.flush();
                } finally {
                    socket.close();
                }
            }
        } finally {
            listener.close();
        }
    }

}

从 Java 服务器向 ESP8266 发送数据

Sending data from Java server to ESP8266

java

sockets

arduino

arduino-esp8266