To exchange data over a datachannel using libdatachannel in C++, we\u2019ll need to set up a signaling server (in Python) to exchange the necessary WebRTC connection information (SDP and ICE candidates), and a STUN\/TURN server using coturn for NAT traversal.<\/p>\n
Install coturn using the package manager and configure it to act as a STUN\/TURN server.<\/p>\n
sudo apt-get install coturn<\/code><\/pre>\nConfigure \/etc\/turnserver.conf with:<\/p>\n
listening-port=3478\nfingerprint\nlt-cred-mech\nuse-auth-secret\nstatic-auth-secret=your-secret-key\nrealm=www.fanyamin.com\nserver-name=www.fanyamin.com<\/code><\/pre>\nStart coturn:<\/p>\n
sudo turnserver -v<\/code><\/pre>\nStep 2: Python Signaling Server<\/h3>\n\n- install library<\/li>\n<\/ul>\n
pip install websockets\n<\/code><\/pre>\nCreate a simple WebSocket signaling server in Python using websockets:<\/p>\n
import asyncio\nimport websockets\nimport json\n\nclients = {}\n\nasync def signaling(websocket, path):\n async for message in websocket:\n data = json.loads(message)\n peer_id = data['peer_id']\n if data['type'] == 'offer' or data['type'] == 'answer':\n recipient = clients.get(data['to'], None)\n if recipient:\n await recipient.send(json.dumps(data))\n elif data['type'] == 'register':\n clients[peer_id] = websocket\n\nasync def main():\n async with websockets.serve(signaling, "0.0.0.0", 8765):\n await asyncio.Future()\n\nasyncio.run(main())<\/code><\/pre>\nThis WebSocket server will exchange SDP and ICE candidates between peers.<\/p>\n
Step 3: C++ Client and Server using libdatachannel<\/h3>\n
You\u2019ll need to install libdatachannel (you can use Conan if you prefer).<\/p>\n
#include <rtc\/rtc.hpp>\n#include <iostream>\n\nvoid setup_peer(rtc::PeerConnection &pc, const std::string &role) {\n \/\/ DataChannel for sending messages\n auto dc = pc.createDataChannel("data");\n\n dc->onOpen([role]() {\n std::cout << role << " DataChannel open!" << std::endl;\n });\n\n dc->onMessage([](std::variant<rtc::binary, std::string> message) {\n if (std::holds_alternative<std::string>(message)) {\n std::cout << "Received message: " << std::get<std::string>(message) << std::endl;\n }\n });\n}\n\nint main() {\n \/\/ Configure STUN server\n rtc::Configuration config;\n config.iceServers.emplace_back("stun:your-stun-server.com");\n\n rtc::PeerConnection pc(config);\n\n setup_peer(pc, "Client");\n\n \/\/ Exchange SDP via signaling server\n pc.onLocalDescription([](rtc::Description desc) {\n std::cout << "Local SDP: " << std::string(desc) << std::endl;\n \/\/ Send SDP to signaling server (use WebSocket)\n });\n\n pc.onGatheringStateChange([](rtc::PeerConnection::GatheringState state) {\n if (state == rtc::PeerConnection::GatheringState::Complete) {\n std::cout << "ICE gathering complete." << std::endl;\n }\n });\n\n \/\/ Connect to signaling server and exchange SDPs and ICE candidates\n \/\/ Implement the signaling logic using WebSockets.\n\n return 0;\n}<\/code><\/pre>\nWorkflow<\/p>\n
\n- Client and Server both connect to the Python signaling server via WebSockets.<\/li>\n
- Client sends an SDP offer through the signaling server.<\/li>\n
- Server responds with an SDP answer.<\/li>\n
- Both peers exchange ICE candidates until a connection is established.<\/li>\n
- Data is exchanged over the DataChannel.<\/li>\n<\/ol>\n
Example<\/h2>\n\n- Use gstreamer to push video <\/li>\n<\/ol>\n
$ gst-launch-1.0 v4l2src device=\/dev\/video0 \\\n! video\/x-raw,width=640,height=480 \\\n! videoconvert ! queue \\\n! x264enc tune=zerolatency bitrate=1000 key-int-max=30 \\\n! video\/x-h264, profile=constrained-baseline \\\n! rtph264pay pt=96 mtu=1200 \\\n! udpsink host=127.0.0.1 port=6000<\/code><\/pre>\n\n- v4l2src \u4ece\u6444\u50cf\u5934\u6355\u83b7\u89c6\u9891\u6d41, \u5206\u8fa8\u7387\u4e3a 640*480<\/li>\n
- x264enc \u5c06\u89c6\u9891\u6d41\u7f16\u7801\u4e3a h264 codec<\/li>\n
- rtph264pay \u5c06\u89c6\u9891\u6d41\u6253\u5305\u4e3a RTP packet<\/li>\n
- udpsink \u5c06 rtp packet \u4ee5 udp \u5305\u53d1\u9001\u51fa\u53bb<\/li>\n<\/ul>\n
\n- Use cpp\/web client to receive the video<\/li>\n<\/ol>\n
\n<!DOCTYPE html>\n<html lang="en">\n<head>\n <meta charset="UTF-8">\n <title>libdatachannel media sender example<\/title>\n<\/head>\n<body>\n\n<p>Please enter the offer provided to you by the sender application: <\/p>\n<textarea cols="80" rows="25"><\/textarea>\n<button>Submit<\/button>\n\n<video id="video-element" muted><\/video>\n\n<script>\n document.querySelector('button').addEventListener('click', async () => {\n const offer = JSON.parse(document.querySelector('textarea').value);\n const pc = new RTCPeerConnection({\n \/\/ Recommended for libdatachannel\n bundlePolicy: 'max-bundle',\n });\n\n pc.onicegatheringstatechange = (state) => {\n if (pc.iceGatheringState === 'complete') {\n \/\/ We only want to provide an answer once all of our candidates have been added to the SDP.\n const answer = pc.localDescription;\n document.querySelector('textarea').value = JSON.stringify({"type": answer.type, sdp: answer.sdp});\n document.querySelector('p').value = 'Please paste the answer in the sender application.';\n alert('Please paste the answer in the sender application.');\n }\n }\n\n pc.ontrack = (evt) => {\n const videoElement = document.getElementById('video-element');\n videoElement.srcObject = evt.streams[0];\n videoElement.play();\n };\n\n await pc.setRemoteDescription(offer);\n\n const answer = await pc.createAnswer();\n await pc.setLocalDescription(answer);\n })\n<\/script>\n\n<\/body>\n<\/html><\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"To exchange data over a datachannel using libdatachannel in C++, we\u2019ll need to set up a signaling server (in Python) to exchange the necessary WebRTC connection information (SDP and ICE candidates), and a STUN\/TURN server using coturn for NAT traversal. components: C++ Client and Server using libdatachannel We\u2019ll use libdatachannel to establish WebRTC peer-to-peer connections. […] →Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-1428","post","type-post","status-publish","format-standard","hentry","category-5"],"_links":{"self":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/1428"}],"collection":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1428"}],"version-history":[{"count":4,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/1428\/revisions"}],"predecessor-version":[{"id":1435,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/1428\/revisions\/1435"}],"wp:attachment":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1428"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1428"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1428"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}