How do I join the SSDP multicast group in Rebol?

I'm trying to listen to SSDP multicast messages such as NOTIFY and SEARCH.

This is my code but I'm not seeing these messages even though wireshark sees them. So, how do I join the SSDP multicast group and receive messages?

Rebol []

attempt [close ssdp]
local-ip: read join dns:// read dns://

ssdp: open/binary udp://:8000
probe group: compose/deep [multicast-groups: [[235.255.255.250 (local-ip)]]]
set-modes ssdp group

forever [
    port: wait [ssdp]
    probe data: copy port
]

The following codes sends a SSDP SEARCH command first to pickup all the devices on the network, and then listens for a SEARCH command from other devices.

REBOL [ 
    Notes: {to listen for SSDP messages.  Works on Rebol2}   
] 

local-ip: read join dns:// read dns:// 

probe local-ip 

attempt [close odata] 
attempt [close idata] 

odata: open/binary udp://239.255.255.250:1900 ; SSDP multicast port address 
set-modes odata [multicast-ttl: 10]
; next line seems unnecessary
; set-modes odata compose/deep [multicast-interface: (local-ip)] 

idata: open/binary udp://:1900 
set-modes idata compose/deep [multicast-groups: [[239.255.255.250 (local-ip)]]] 

ST: "ssdp:all" 
MX: 3 

insert odata rejoin [ 
         {M-SEARCH * HTTP/1.1} crlf 
         {HOST: 239.255.255.250:1900} crlf 
         {MAN: "ssdp:discover"} crlf 
         {MX: } MX crlf 
         {ST: } ST crlf 
         crlf 
] 

forever [ 
    port: wait [odata idata] 
    data: copy port 
    if find/part data {M-SEARCH} 8 [
        print "SSDP search issued from:"
        print [ "Address: " port/remote-ip]
        print [ "On port: " port/remote-port]
    ]
    probe data
]