diff --git a/modules/libcom/test/osiSockTest.c b/modules/libcom/test/osiSockTest.c
index 6672cdbd3..39777fc10 100644
--- a/modules/libcom/test/osiSockTest.c
+++ b/modules/libcom/test/osiSockTest.c
@@ -77,15 +77,76 @@ void udpSockTest(void)
 }
 
 
+static
+int doBind(int expect, SOCKET S, unsigned* port)
+{
+    osiSockAddr addr;
+    int ret;
+
+    memset(&addr, 0, sizeof(addr));
+    addr.ia.sin_family = AF_INET;
+    addr.ia.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+    addr.ia.sin_port = htons(*port);
+
+    ret = bind(S, &addr.sa, sizeof(addr.ia));
+    if(ret) {
+        testOk(expect==1, "bind() to %u error %d, %d", *port, ret, SOCKERRNO);
+        return 1;
+    } else {
+        osiSocklen_t slen = sizeof(addr);
+        ret = getsockname(S, &addr.sa, &slen);
+        if(ret) {
+            testFail("Unable to find sock name after binding");
+            return 1;
+        } else {
+            *port = ntohs(addr.ia.sin_port);
+            testOk(expect==0, "bind() to port %u", *port);
+            return 0;
+        }
+    }
+}
+
+void udpSockFanoutTest(void)
+{
+    SOCKET A, B, C;
+    unsigned port=0; /* choose random port */
+
+    A = epicsSocketCreate(AF_INET, SOCK_DGRAM, 0);
+    B = epicsSocketCreate(AF_INET, SOCK_DGRAM, 0);
+    C = epicsSocketCreate(AF_INET, SOCK_DGRAM, 0);
+
+    if(A==INVALID_SOCKET || B==INVALID_SOCKET || C==INVALID_SOCKET)
+        testAbort("Insufficient sockets");
+
+    /* not A */
+    epicsSocketEnableAddressUseForDatagramFanout(B);
+    epicsSocketEnableAddressUseForDatagramFanout(C);
+
+    testDiag("First test if epicsSocketEnableAddressUseForDatagramFanout() is necessary");
+
+    doBind(0, A, &port);
+    doBind(1, B, &port); /* expect failure */
+
+    epicsSocketDestroy(A);
+
+    testDiag("Now the real test");
+    doBind(0, B, &port);
+    doBind(0, C, &port);
+
+    epicsSocketDestroy(B);
+    epicsSocketDestroy(C);
+}
+
 MAIN(osiSockTest)
 {
     int status;
-    testPlan(14);
+    testPlan(18);
 
     status = osiSockAttach();
     testOk(status, "osiSockAttach");
 
     udpSockTest();
+    udpSockFanoutTest();
 
     osiSockRelease();
     return testDone();