run libzmq with pgm in win10,but abort with error

[choujayyl]

Issue description

run libzmq with openpgm in win10,but abort with error·。

Error: Join multicast group { .gr_interface = 0, .gr_group = "224.0.22.1" } failed: Invalid argument.(10022)
Invalid argument (G:\dev\2021\daspnetsrv2\testPGM\lib\src\zeromq-4.3.3\src\session_base.cpp:734)

Environment

• libzmq version (commit hash if unreleased): 4.3.4
• OS: win10
• openpgm v5.2.128

Minimal test code / Steps to reproduce the issue

1. `#include <string.h>
   #include <windows.h>
   #include <zmq.h>
   int main()
   {
   int index = 0;
   int count = -1;
   char buf[128];
   void* context = zmq_ctx_new();
   void* socket = zmq_socket(context, ZMQ_SUB);
   zmq_setsockopt(socket, ZMQ_SUBSCRIBE, "", 0);
   int rc = zmq_connect(socket, "epgm://224.0.22.1:9210");
   if (rc != 0)
   {
   printf("zmq_errno() is %d,:%s\n", zmq_errno(),zmq_strerror(zmq_errno()));
   return -1;
   }

   while (1) {
   sprintf_s(buf, sizeof(buf),"%d -- SERVER MSG!", index++);
   count = zmq_send(socket, buf, strlen(buf), 0);
   printf("%s (%d)\r\n", buf, count);
   Sleep(1000);
   }

   zmq_close(socket);
   zmq_ctx_destroy(context);
   return 0;
   }
   `

What's the actual result? (include assertion message & call stack if applicable)

Error: Join multicast group { .gr_interface = 0, .gr_group = "224.0.22.1" } failed: Invalid argument.(10022)
Invalid argument (G:\dev\2021\daspnetsrv2\testPGM\lib\src\zeromq-4.3.3\src\session_base.cpp:734)

What's the expected result?

No error.

[choujayyl]

I found reason,because openPGM use setsockopt with SOL_IP option.That indicate Invaild parameter。You must use IPPROTO_IP. But I dont understand.

[RRRaymond]

Awesome, your solution save me at least 2 days.

[jinspace]

it matters.