Separate lower-level API into separate packages.

ssdp/ssdp.go

@@ -0,0 +1,78 @@
+package ssdp
+
+import (
+	"errors"
+	"log"
+	"net/http"
+	"net/url"
+	"strconv"
+	"time"
+
+	"github.com/huin/goupnp/httpu"
+)
+
+const (
+	ssdpDiscover = `"ssdp:discover"`
+	methodSearch = "M-SEARCH"
+	ssdpUDP4Addr = "239.255.255.250:1900"
+)
+
+// 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 *httpu.HTTPUClient, searchTarget string, maxWaitSeconds int, numSends int) ([]*http.Response, error) {
+	if maxWaitSeconds < 1 {
+		return nil, errors.New("ssdp: maxWaitSeconds must be >= 1")
+	}
+
+	seenUsns := make(map[string]bool)
+	var responses []*http.Response
+	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
+	}
+	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"); st != searchTarget {
+			log.Printf("ssdp: got unexpected search target result %q", st)
+			return nil, nil
+		}
+		location, err := response.Location()
+		if err != nil {
+			log.Printf("ssdp: no usable location in search response (discarding): %v", err)
+			continue
+		}
+		usn := response.Header.Get("USN")
+		if usn == "" {
+			log.Printf("ssdp: empty/missing USN in search response (using location instead): %v", err)
+			usn = location.String()
+		}
+		if _, alreadySeen := seenUsns[usn]; !alreadySeen {
+			seenUsns[usn] = true
+			responses = append(responses, response)
+		}
+	}
+
+	return responses, nil
+}