Modified func Close in pkg/isapi/client.go to call '/ISAPI/System/TwoWayAudio/channels/<channel id>/close' instead of '/ISAPI/System/TwoWayAudio/channels/<channel id/close/open'

Modified pkg/isapi/client.go to call 'close' before 'open' to prevent channel left open from prior connection blocking with 401 or 403 errors.

pkg/isapi/client.go

@@ -86,12 +86,28 @@ func (c *Client) Dial() (err error) {
 func (c *Client) Open() (err error) {
 	link := c.url + "/ISAPI/System/TwoWayAudio/channels/" + c.channel
 
-	req, err := http.NewRequest("PUT", link+"/open", nil)
+   // Hikvision ISAPI may not accept a new open request if the previous one was not closed (e.g.
+   // using the test button on-camera or via curl command) but a close request can be sent even if
+   // the audio is already closed. So, we send a close request first and then open it again. Seems
+   // janky but it works.
+	req, err := http.NewRequest("PUT", link+"/close", nil)
 	if err != nil {
 		return err
 	}
 
 	res, err := tcp.Do(req)
+	if err != nil {
+		return err
+	}
+
+	tcp.Close(res)
+
+	req, err = http.NewRequest("PUT", link+"/open", nil)
+	if err != nil {
+		return err
+	}
+
+	res, err = tcp.Do(req)
 	if err != nil {
 		return
 	}
@@ -124,8 +140,8 @@ func (c *Client) Open() (err error) {
 }
 
 func (c *Client) Close() (err error) {
-	link := c.url + "/ISAPI/System/TwoWayAudio/channels/" + c.channel + "/close"
-	req, err := http.NewRequest("PUT", link+"/open", nil)
+	link := c.url + "/ISAPI/System/TwoWayAudio/channels/" + c.channel
+	req, err := http.NewRequest("PUT", link+"/close", nil)
 	if err != nil {
 		return err
 	}

pkg/tcp/request.go

@@ -115,7 +115,9 @@ func Do(req *http.Request) (*http.Response, error) {
 			)
 		case "auth":
 			nc := "00000001"
-			cnonce := "00000001" // TODO: random...
+			// TODO: Random cnonce
+         // Here is temp static cnonce of required 32 bytes
+			cnonce := "ZDlmODczZTk2NjQyZTQ4OGQ5ZGEzOTI3YTc5Y2Q0ZGM="
 			response := HexMD5(ha1, nonce, nc, cnonce, qop, ha2)
 			header = fmt.Sprintf(
 				`Digest username="%s", realm="%s", nonce="%s", uri="%s", qop=%s, nc=%s, cnonce="%s", response="%s"`,