ESP8266 doesn't receive packets in WIFI network

Question

While running the UDP example on my node mcu v3.0 I encountered the following strange problem.

If I connect both my computer and the node mcu to a WIFI-hotspot hosted by my phone everything runs perfectly (I can send udp packets from my computer via netcat to the node mcu and get an answer).

However if I switch to the WiFi-network provided by the student residence where Im living (we have to connect to the next router with corresponding ssid and password like for any other normal wifi network) the node mcu doesn't receive any packets at all (it still prints out an IP address so I guess it could connect to the network). I also tried sending udp packets from my computer to my laptop via netcat, which stills works normally. What's going on here?

Here's the code:

/*
  UDPSendReceive.pde:
  This sketch receives UDP message strings, prints them to the serial port
  and sends an "acknowledge" string back to the sender

  A Processing sketch is included at the end of file that can be used to send
  and received messages for testing with a computer.

  created 21 Aug 2010
  by Michael Margolis

  This code is in the public domain.

  adapted from Ethernet library examples
*/


#include <ESP8266WiFi.h>
#include <WiFiUdp.h>

#ifndef STASSID
#define STASSID ".."
#define STAPSK  ".."
#endif

unsigned int localPort = 8888;      // local port to listen on

// buffers for receiving and sending data
char packetBuffer[UDP_TX_PACKET_MAX_SIZE + 1]; //buffer to hold incoming packet,
char  ReplyBuffer[] = "acknowledged\r\n";       // a string to send back

WiFiUDP Udp;

void setup() {
  Serial.begin(115200);
  WiFi.mode(WIFI_STA);
  WiFi.begin(STASSID, STAPSK);
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print('.');
    delay(500);
  }
  Serial.print("Connected! IP address: ");
  Serial.println(WiFi.localIP());
  Serial.printf("UDP server on port %d\n", localPort);
  Udp.begin(localPort);
}

void loop() {
  // if there's data available, read a packet
  int packetSize = Udp.parsePacket();
  if (packetSize) {
    Serial.printf("Received packet of size %d from %s:%d\n    (to %s:%d, free heap = %d B)\n",
                  packetSize,
                  Udp.remoteIP().toString().c_str(), Udp.remotePort(),
                  Udp.destinationIP().toString().c_str(), Udp.localPort(),
                  ESP.getFreeHeap());

    // read the packet into packetBufffer
    int n = Udp.read(packetBuffer, UDP_TX_PACKET_MAX_SIZE);
    packetBuffer[n] = 0;
    Serial.println("Contents:");
    Serial.println(packetBuffer);

    // send a reply, to the IP address and port that sent us the packet we received
    Udp.beginPacket(Udp.remoteIP(), Udp.remotePort());
    Udp.write(ReplyBuffer);
    Udp.endPacket();
  }

}

/*
  test (shell/netcat):
  --------------------
      nc -u 192.168.esp.address 8888
*/

EDIT: Calling a website (like google) from the node mcu works fine

WAPs can be configured to disallow node-to-node communication. You should ask the network administrator. — Ron Maupin
Today it worked for like half an hour. But normally ping fails as well — user2224350

Dario Dario · Accepted Answer · 2019-12-08T11:47:07

Most likely you will have to add IO firewall rules. Check This link.

Or by using PowerShell:

PS C:\> New-NetFirewallRule -DisplayName "Allow UDP 8888 over Teredo" -Direction Inbound -Action Allow -EdgeTraversalPolicy Allow -Protocol UDP -LocalPort 8888 -Program "C:\Program Files (x86)\TestIPv6App.exe"

ESP8266 doesn't receive packets in WIFI network

1 Answers