package ssdp import ( "errors" "log" "net/http" "net/url" "strconv" "time" ) const ( ssdpDiscover = `"ssdp:discover"` ntsAlive = `ssdp:alive` ntsByebye = `ssdp:byebye` ntsUpdate = `ssdp:update` ssdpUDP4Addr = "239.255.255.250:1900" ssdpSearchPort = 1900 methodSearch = "M-SEARCH" methodNotify = "NOTIFY" // SSDPAll is a value for searchTarget that searches for all devices and services. SSDPAll = "ssdp:all" // UPNPRootDevice is a value for searchTarget that searches for all root devices. UPNPRootDevice = "upnp:rootdevice" ) // HTTPUClient is the interface required to perform HTTP-over-UDP requests. type HTTPUClient interface { Do( req *http.Request, timeout time.Duration, numSends int, ) ([]*http.Response, error) } // SSDPRawSearch performs a fairly raw SSDP search request, and returns the // unique response(s) that it receives. Each response has the requested // searchTarget, a USN, and a valid location. maxWaitSeconds states how long to // wait for responses in seconds, and must be a minimum of 1 (the // implementation waits an additional 100ms for responses to arrive), 2 is a // reasonable value for this. numSends is the number of requests to send - 3 is // a reasonable value for this. func SSDPRawSearch( httpu HTTPUClient, searchTarget string, maxWaitSeconds int, numSends int, ) ([]*http.Response, error) { if maxWaitSeconds < 1 { return nil, errors.New("ssdp: maxWaitSeconds must be >= 1") } req := http.Request{ Method: methodSearch, // TODO: Support both IPv4 and IPv6. Host: ssdpUDP4Addr, URL: &url.URL{Opaque: "*"}, Header: http.Header{ // Putting headers in here avoids them being title-cased. // (The UPnP discovery protocol uses case-sensitive headers) "HOST": []string{ssdpUDP4Addr}, "MX": []string{strconv.FormatInt(int64(maxWaitSeconds), 10)}, "MAN": []string{ssdpDiscover}, "ST": []string{searchTarget}, }, } allResponses, err := httpu.Do(&req, time.Duration(maxWaitSeconds)*time.Second+100*time.Millisecond, numSends) if err != nil { return nil, err } isExactSearch := searchTarget != SSDPAll && searchTarget != UPNPRootDevice seenIDs := make(map[string]bool) var responses []*http.Response for _, response := range allResponses { if response.StatusCode != 200 { log.Printf("ssdp: got response status code %q in search response", response.Status) continue } if st := response.Header.Get("ST"); isExactSearch && st != searchTarget { continue } usn := response.Header.Get("USN") loc, err := response.Location() if err != nil { // No usable location in search response - discard. continue } id := loc.String() + "\x00" + usn if _, alreadySeen := seenIDs[id]; !alreadySeen { seenIDs[id] = true responses = append(responses, response) } } return responses, nil }