Cameradar v4 (#212)

* Refactor of cameradar library

* Old unit tests updated & improved. New unit tests inc

* Update documentation & issue template

* Update dependencies

* Update TravisCI build script to reflect argument change

* Remove outdated contributing guide

* Update README with more examples and remove part on library

* Add second camera to Travis build script & improve error detection

* Fix typo in travis script & add missing image to readme

* Remember that travis uses bash syntax not fish

* Use relative paths for images in the README

scan.go

@@ -0,0 +1,70 @@
+package cameradar
+
+import (
+	"strings"
+
+	"github.com/ullaakut/nmap"
+)
+
+// Scan scans the target networks and tries to find RTSP streams within them.
+//
+// targets can be:
+//
+//    - a subnet (e.g.: 172.16.100.0/24)
+//    - an IP (e.g.: 172.16.100.10)
+//    - a hostname (e.g.: localhost)
+//    - a range of IPs (e.g.: 172.16.100.10-20)
+//
+// ports can be:
+//
+//    - one or multiple ports and port ranges separated by commas (e.g.: 554,8554-8560,18554-28554)
+func (s *Scanner) Scan() ([]Stream, error) {
+	s.term.StartStep("Scanning the network")
+
+	// Run nmap command to discover open ports on the specified targets & ports.
+	nmapScanner, err := nmap.NewScanner(
+		nmap.WithTargets(s.targets...),
+		nmap.WithPorts(s.ports...),
+		nmap.WithTimingTemplate(nmap.Timing(s.speed)),
+	)
+	if err != nil {
+		return nil, s.term.FailStepf("unable to create network scanner: %v", err)
+	}
+
+	return s.scan(nmapScanner)
+}
+
+func (s *Scanner) scan(nmapScanner nmap.ScanRunner) ([]Stream, error) {
+	results, err := nmapScanner.Run()
+	if err != nil {
+		return nil, s.term.FailStepf("error while scanning network: %v", err)
+	}
+
+	// Get streams from nmap results.
+	var streams []Stream
+	for _, host := range results.Hosts {
+		for _, port := range host.Ports {
+			if port.Status() != "open" {
+				continue
+			}
+
+			if !strings.Contains(port.Service.Name, "rtsp") {
+				continue
+			}
+
+			for _, address := range host.Addresses {
+				streams = append(streams, Stream{
+					Device:  port.Service.Product,
+					Address: address.Addr,
+					Port:    port.ID,
+				})
+			}
+		}
+	}
+
+	s.term.Debugf("Found %d RTSP streams\n", len(streams))
+
+	s.term.EndStep()
+
+	return streams, nil
+}