作者記：由于項(xiàng)目需要在瀏覽器和安卓手機(jī)之間建立p2p連接，自然就想到了使用WebRTC，經(jīng)過(guò)一周多的摸索，在瀏覽器端能成功實(shí)時(shí)顯示手機(jī)屏幕，但是會(huì)有卡頓、延遲等現(xiàn)象，試過(guò)了很多辦法，效果不理想，遂擱置，現(xiàn)在把期間踩過(guò)的坑和出現(xiàn)的問(wèn)題記錄一下，供后來(lái)人參考，如果有解決方案，歡迎評(píng)論。
坑1：
WebRTC建立p2p連接的過(guò)程中，需要交換雙方的SDP，安卓端使用的是implementation'org.webrtc:google-webrtc:1.0.30039'，它的SDP格式是
package org.webrtc;
import java.util.Locale;
public class SessionDescription {
public final SessionDescription.Type type;
public final String description;
...
}
瀏覽器JS端的SDP格式是
sdp: "v=0\r\no=- 1123295340288612068 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=group:BUNDLE audio video data\r\na=msid-semantic: WMS\r\nm=audio 9 UDP/TLS/RTP/SAVPF 111 103 104 9 0 8 106 105 13 110 112 113 126\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=ice-ufrag:mkpU\r\na=ice-pwd:PxbO3d1s7zsoo3d3x7U4izWi\r\na=ice-options:trickle\r\na=fingerprint:sha-256 60:73:22:62:4C:04:31:6A:41:A6:C3:F5:9A:57:76:B2:B6:A3:40:6E:86:48:F9:79:C7:DA:0E:46:BD:A9:B6:85\r\na=setup:active\r\na=mid:audio\r\na=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level\r\na=extmap:2 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\na=extmap:3 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01\r\na=inactive\r\na=rtcp-mux\r\na=rtpmap:111 opus/48000/2\r\na=rtcp-fb:111 transport-cc\r\na=fmtp:111 minptime=10;useinbandfec=1\r\na=rtpmap:103 ISAC/16000\r\na=rtpmap:104 ISAC/32000\r\na=rtpmap:9 G722/8000\r\na=rtpmap:0 PCMU/8000\r\na=rtpmap:8 PCMA/8000\r\na=rtpmap:106 CN/32000\r\na=rtpmap:105 CN/16000\r\na=rtpmap:13 CN/8000\r\na=rtpmap:110 telephone-event/48000\r\na=rtpmap:112 telephone-event/32000\r\na=rtpmap:113 telephone-event/16000\r\na=rtpmap:126 telephone-event/8000\r\nm=video 9 UDP/TLS/RTP/SAVPF 96 97 98 99 100 101 127\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=ice-ufrag:mkpU\r\na=ice-pwd:PxbO3d1s7zsoo3d3x7U4izWi\r\na=ice-options:trickle\r\na=fingerprint:sha-256 60:73:22:62:4C:04:31:6A:41:A6:C3:F5:9A:57:76:B2:B6:A3:40:6E:86:48:F9:79:C7:DA:0E:46:BD:A9:B6:85\r\na=setup:active\r\na=mid:video\r\na=extmap:14 urn:ietf:params:rtp-hdrext:toffset\r\na=extmap:2 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\na=extmap:13 urn:3gpp:video-orientation\r\na=extmap:3 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01\r\na=extmap:5 http://www.webrtc.org/experiments/rtp-hdrext/playout-delay\r\na=extmap:6 http://www.webrtc.org/experiments/rtp-hdrext/video-content-type\r\na=extmap:7 http://www.webrtc.org/experiments/rtp-hdrext/video-timing\r\na=extmap:9 http://www.webrtc.org/experiments/rtp-hdrext/color-space\r\na=recvonly\r\na=rtcp-mux\r\na=rtcp-rsize\r\na=rtpmap:96 VP8/90000\r\na=rtcp-fb:96 goog-remb\r\na=rtcp-fb:96 transport-cc\r\na=rtcp-fb:96 ccm fir\r\na=rtcp-fb:96 nack\r\na=rtcp-fb:96 nack pli\r\na=rtpmap:97 rtx/90000\r\na=fmtp:97 apt=96\r\na=rtpmap:98 VP9/90000\r\na=rtcp-fb:98 goog-remb\r\na=rtcp-fb:98 transport-cc\r\na=rtcp-fb:98 ccm fir\r\na=rtcp-fb:98 nack\r\na=rtcp-fb:98 nack pli\r\na=fmtp:98 profile-id=0\r\na=rtpmap:99 rtx/90000\r\na=fmtp:99 apt=98\r\na=rtpmap:100 red/90000\r\na=rtpmap:101 rtx/90000\r\na=fmtp:101 apt=100\r\na=rtpmap:127 ulpfec/90000\r\nm=application 9 UDP/DTLS/SCTP webrtc-datachannel\r\nc=IN IP4 0.0.0.0\r\na=ice-ufrag:mkpU\r\na=ice-pwd:PxbO3d1s7zsoo3d3x7U4izWi\r\na=ice-options:trickle\r\na=fingerprint:sha-256 60:73:22:62:4C:04:31:6A:41:A6:C3:F5:9A:57:76:B2:B6:A3:40:6E:86:48:F9:79:C7:DA:0E:46:BD:A9:B6:85\r\na=setup:active\r\na=mid:data\r\na=sctp-port:5000\r\na=max-message-size:262144\r\n"
type: "answer"
__proto__: Object
所以二者在通過(guò)信令服務(wù)器交換SDP時(shí)，需要轉(zhuǎn)換格式以匹配對(duì)端的SDP。
坑2：
瀏覽器側(cè)是強(qiáng)制開(kāi)啟安全指紋的，而安卓端可以關(guān)閉安全指紋，如果安卓端關(guān)閉了安全指紋，那么在交換SDP的時(shí)候，瀏覽器側(cè)在調(diào)用setRemoteDesription()方法時(shí)會(huì)報(bào)錯(cuò)。
注意：只有在正確調(diào)用peerConnection.setRemoteDescription()成功后，才會(huì)觸發(fā)peerConnection.onicecandidate回調(diào)，所以一定要保證兩端SDP一致。
解決辦法：安卓端也必須開(kāi)啟安全指紋
PeerConnectionFactory.Options options = new PeerConnectionFactory.Options();
options.disableEncryption = false; //或者不設(shè)置。當(dāng)設(shè)置為true時(shí)，SDP包將會(huì)沒(méi)有fingerprint
