<p></p>
<p>I used the following patch</p>
<div class="highlight highlight-source-diff"><pre><span class="pl-c1">diff --git a/examples/gnrc_networking/udp.c b/examples/gnrc_networking/udp.c</span>
index 54f00afd7e..e72e026c63 100644
<span class="pl-md">--- a/examples/gnrc_networking/udp.c</span>
<span class="pl-mi1">+++ b/examples/gnrc_networking/udp.c</span>
<span class="pl-mdr">@@ -36,7 +36,7 @@</span> static gnrc_netreg_entry_t server = GNRC_NETREG_ENTRY_INIT_PID(GNRC_NETREG_DEMUX
                                                                KERNEL_PID_UNDEF);
 
 
<span class="pl-md"><span class="pl-md">-</span>static void send(char *addr_str, char *port_str, char *data, unsigned int num,</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>static void send(char *addr_str, char *port_str, const char *data, unsigned int num,</span>
                  unsigned int delay)
 {
     gnrc_netif_t *netif = NULL;
<span class="pl-mdr">@@ -149,7 +149,7 @@</span> static void stop_server(void)
 int udp_cmd(int argc, char **argv)
 {
     if (argc < 2) {
<span class="pl-md"><span class="pl-md">-</span>        printf("usage: %s [send|server]\n", argv[0]);</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>        printf("usage: %s [send|server|const]\n", argv[0]);</span>
         return 1;
     }
 
<span class="pl-mdr">@@ -169,6 +169,23 @@</span> int udp_cmd(int argc, char **argv)
         }
         send(argv[2], argv[3], argv[4], num, delay);
     }
<span class="pl-mi1"><span class="pl-mi1">+</span>    else if (strcmp(argv[1], "const") == 0) {</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>        uint32_t num = 1;</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>        uint32_t delay = 1000000;</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>        if (argc < 4) {</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>            printf("usage: %s send <addr> <port> [<num> [<delay in us>]]\n",</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>                   argv[0]);</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>            return 1;</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>        }</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>        if (argc > 4) {</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>            num = atoi(argv[4]);</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>        }</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>        if (argc > 5) {</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>            delay = atoi(argv[5]);</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>        }</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>        const char *data = "Hallo world!";</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>        send(argv[2], argv[3], data, num, delay);</span>
<span class="pl-mi1"><span class="pl-mi1">+</span>    }</span>
     else if (strcmp(argv[1], "server") == 0) {
         if (argc < 3) {
             printf("usage: %s server [start|stop]\n", argv[0]);</pre></div>
<p>flashed <code>examples/gnrc_networking</code> to a Nucleo-F767ZI and did the following:</p>
<pre><code>2021-06-09 09:17:47,217 # udp const fe80::.... 12345
2021-06-09 09:17:47,223 # Success: sent 12 byte(s) to [fe80::....]:12345
</code></pre>
<p>With Wireshark, I can see a valid UDP datagram being received that contains "Hello world!" as payload. The Ethernet peripheral for STM32 is as far as I know identical for all STM32 MCUs. So that should also work on F4.</p>
<p><a class="user-mention" data-hovercard-type="user" data-hovercard-url="/users/kex2017/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://github.com/kex2017">@kex2017</a> Could you provide the exact source code so that I can try to reproduce? If it is based on an example program, you can just provide the output of <code>git diff</code> here.</p>

<p style="font-size:small;-webkit-text-size-adjust:none;color:#666;">—<br />You are receiving this because you are subscribed to this thread.<br />Reply to this email directly, <a href="https://github.com/RIOT-OS/RIOT/issues/16541#issuecomment-857454502">view it on GitHub</a>, or <a href="https://github.com/notifications/unsubscribe-auth/ABE7WYCLDYNEPWLAFRTFQFLTR4JGPANCNFSM46LLC56A">unsubscribe</a>.<img src="https://github.com/notifications/beacon/ABE7WYG6OHJ7UB7CL6GMNJLTR4JGPA5CNFSM46LLC56KYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOGMN3PJQ.gif" height="1" width="1" alt="" /></p>
<script type="application/ld+json">[
{
"@context": "http://schema.org",
"@type": "EmailMessage",
"potentialAction": {
"@type": "ViewAction",
"target": "https://github.com/RIOT-OS/RIOT/issues/16541#issuecomment-857454502",
"url": "https://github.com/RIOT-OS/RIOT/issues/16541#issuecomment-857454502",
"name": "View Issue"
},
"description": "View this Issue on GitHub",
"publisher": {
"@type": "Organization",
"name": "GitHub",
"url": "https://github.com"
}
}
]</script>