<blockquote>
<p>(I took the freedom to edit OP for better readability)</p>
</blockquote>
<p>Thanks for your help.</p>
<blockquote>
<p><a class="user-mention" data-hovercard-type="user" data-hovercard-url="/hovercards?user_id=675644" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://github.com/miri64">@miri64</a></p>
<blockquote>
<p>I took the freedom to edit OP for better readability</p>
</blockquote>
<p>Thanks, <a class="user-mention" data-hovercard-type="user" data-hovercard-url="/hovercards?user_id=22351514" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://github.com/mmaxus35">@mmaxus35</a> has still problems with the markup language <g-emoji class="g-emoji" alias="wink" fallback-src="https://github.githubassets.com/images/icons/emoji/unicode/1f609.png">😉</g-emoji></p>
<p>Yes, the current ESP8266 port has problems with the <code>lwIP</code> package. That's why all ESP8266 boards are blacklisted. BTW, with the complete reimplementation of the ESP8266 port in PR <a class="issue-link js-issue-link" data-error-text="Failed to load issue title" data-id="417357236" data-permission-text="Issue title is private" data-url="https://github.com/RIOT-OS/RIOT/issues/11108" data-hovercard-type="pull_request" data-hovercard-url="/RIOT-OS/RIOT/pull/11108/hovercard" href="https://github.com/RIOT-OS/RIOT/pull/11108">#11108</a> which is waiting for review, it will not be a problem any longer.</p>
<p>But, there shouldn't be any problem with ESP32 and <code>lwIP</code>. The problem seems not to be related to the ESP32 board. According to <a class="user-mention" data-hovercard-type="user" data-hovercard-url="/hovercards?user_id=22351514" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://github.com/mmaxus35">@mmaxus35</a>, the board has WiFi connectivity. He can ping the board and the UDP lwIP socket example works.</p>
<p><a class="user-mention" data-hovercard-type="user" data-hovercard-url="/hovercards?user_id=22351514" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://github.com/mmaxus35">@mmaxus35</a> Are you sure that your TCP server is running on <code>fe80::4c2c:2f99:9ae8:73cb</code> and is listening at port <code>12345</code>? Can you see an according entry when you use command</p>
<pre><code>netstat -tulpen
</code></pre>
<p>on this machine?</p>
</blockquote>
<p>Of course, fe80::4c2c:2f99:9ae8:73cb is running in Java in my Windows PC adnd i can send packets using another programs like "Packet Sender" and they are received and messages displayed to screen. Here is the java code that i use</p>
<pre><code> import java.io.*;
import java.net.*;
 
class TCPServer
{
         String capitalizedSentence;
   public static void main(String argv[]) throws Exception
      {
         String clientSentence;
         String capitalizedSentence;
         ServerSocket welcomeSocket = new ServerSocket(12345);

 
         while(true)
         {
            Socket connectionSocket = welcomeSocket.accept();
            BufferedReader inFromClient =
               new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
            DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
            clientSentence = inFromClient.readLine();
            System.out.println("Received: " + clientSentence);
            capitalizedSentence = clientSentence.toUpperCase() + '\n';
            outToClient.writeBytes(capitalizedSentence);
         }
      }
}
</code></pre>

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