问题描述
在同一草图中同时使用TCP和UDP时遇到问题。似乎发生的情况是，如果在将同一套接字用于TCP之后重用于UDP，则UPD无法接收数据。我能够通过WebServer示例重现此内容。我每10秒添加一次DNS查询，以查询yahoo.com IP地址。如果我没有从浏览器创建任何客户端流量，则DSN查询成功。通过HTTP over TCP查询服务器后，DSN查询开始失败。 DNS查询在UDP中实现。这是我正在使用的代码：
/*
Web Server
A simple web server that shows the value of the analog input pins.
using an Arduino Wiznet Ethernet shield.
Circuit:
* Ethernet shield attached to pins 10,11,12,13
* Analog inputs attached to pins A0 through A5 (optional)
created 18 Dec 2009
by David A. Mellis
modified 9 Apr 2012
by Tom Igoe
modified 02 Sept 2015
by Arturo Guadalupi
*/
#include <SPI.h>
#include <Ethernet.h>
#include <Dns.h>
// Enter a MAC address and IP address for your controller below.
// The IP address will be dependent on your local network:
byte mac[] = {
0xDE,0xAD,0xBE,0xEF,0xFE,0xED
};
IPAddress ip(192,168,1,177);
// Initialize the Ethernet server library
// with the IP address and port you want to use
// (port 80 is default for HTTP):
EthernetServer server(80);
unsigned long t0;
void setup() {
// You can use Ethernet.init(pin) to configure the CS pin
//Ethernet.init(10); // Most Arduino shields
//Ethernet.init(5); // MKR ETH shield
//Ethernet.init(0); // Teensy 2.0
//Ethernet.init(20); // Teensy++ 2.0
//Ethernet.init(15); // ESP8266 with Adafruit Featherwing Ethernet
//Ethernet.init(33); // ESP32 with Adafruit Featherwing Ethernet
// Open serial communications and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}
Serial.println("Ethernet WebServer Example");
// start the Ethernet connection and the server:
Ethernet.begin(mac,ip);
// Check for Ethernet hardware present
if (Ethernet.hardwareStatus() == EthernetNoHardware) {
Serial.println("Ethernet shield was not found. Sorry,can't run without hardware. :(");
while (true) {
delay(1); // do nothing,no point running without Ethernet hardware
}
}
if (Ethernet.linkStatus() == LinkOFF) {
Serial.println("Ethernet cable is not connected.");
}
// start the server
server.begin();
Serial.print("server is at ");
Serial.println(Ethernet.localIP());
t0 = millis();
}
void loop() {
// listen for incoming clients
EthernetClient client = server.available();
if (client) {
Serial.println("new client");
// an http request ends with a blank line
boolean currentLineIsBlank = true;
while (client.connected()) {
if (client.available()) {
char c = client.read();
// if you've gotten to the end of the line (received a newline
// character) and the line is blank,the http request has ended,// so you can send a reply
if (c == '\n' && currentLineIsBlank) {
// send a standard http response header
client.println("HTTP/1.1 200 OK");
client.println("Content-Type: text/html");
client.println("Connection: close"); // the connection will be closed after completion of the response
client.println("Refresh: 5"); // refresh the page automatically every 5 sec
client.println();
client.println("<!DOCTYPE HTML>");
client.println("<html>");
// output the value of each analog input pin
for (int analogChannel = 0; analogChannel < 6; analogChannel++) {
int sensorReading = analogRead(analogChannel);
client.print("analog input ");
client.print(analogChannel);
client.print(" is ");
client.print(sensorReading);
client.println("<br />");
}
client.println("</html>");
break;
}
if (c == '\n') {
// you're starting a new line
currentLineIsBlank = true;
} else if (c != '\r') {
// you've gotten a character on the current line
currentLineIsBlank = false;
}
}
}
// give the web browser time to receive the data
delay(1);
// close the connection:
client.stop();
Serial.println("client disconnected");
}
if (millis() - t0 > 10000)
{
DNSClient dns;
dns.begin(IPAddress(8,8,8));
IPAddress yahoo;
if (dns.getHostByName("yahoo.com",yahoo) == 1)
{
Serial.print("Yahoo: ");
Serial.print(yahoo[0]);
Serial.print(".");
Serial.print(yahoo[1]);
Serial.print(".");
Serial.print(yahoo[2]);
Serial.print(".");
Serial.println(yahoo[3]);
}
else
{
Serial.println("Failed to query yahoo.com IP address");
}
t0 = millis();
}
}
这是一个已知问题吗？有人可以帮忙找出我的代码中的问题，或者有解决此问题的方法吗？可能是硬件问题吗？我使用的是SunFounder开发板，而不是原始的Arduino开发板。
非常感谢， 波阿斯，
解决方法
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