libwebrtc - Pure C WebRTC Library

A lightweight, cross-platform WebRTC implementation in pure C.

Features

• Pure C99 implementation - No C++ dependencies
• Cross-platform - Linux, macOS, Windows, FreeBSD
• Full protocol stack:
  • ICE/STUN/TURN for connectivity
  • DTLS for key exchange
  • SRTP for media encryption
  • SCTP for data channels
  • SDP parsing and generation
• Platform abstraction layer for portability
• Minimal dependencies - Only standard C library
• Simple API design - Easy to integrate

Architecture

libwebrtc/
├── include/          # Public API headers
│   ├── webrtc.h              # Main API
│   ├── webrtc_platform.h     # Platform abstraction
│   ├── webrtc_ice.h          # ICE protocol
│   ├── webrtc_stun.h         # STUN protocol
│   ├── webrtc_sdp.h          # SDP parser
│   ├── webrtc_dtls.h         # DTLS security
│   ├── webrtc_srtp.h         # SRTP encryption
│   └── webrtc_sctp.h         # SCTP transport
├── src/
│   ├── api/          # PeerConnection API
│   ├── platform/     # Platform implementations
│   ├── net/          # Network layer (STUN)
│   └── transport/    # Transport protocols (ICE/DTLS/SRTP/SCTP/SDP)
├── examples/         # Example applications
└── tests/            # Unit tests

See ARCHITECTURE.md for detailed design documentation.

Building

Linux/macOS

# Using CMake
mkdir build && cd build
cmake ..
make

# Or using Make directly
make

Windows

mkdir build && cd build
cmake -G "Visual Studio 16 2019" ..
cmake --build .

Quick Start

#include "webrtc.h"

static void on_ice_candidate(webrtc_peer_connection_t *pc, 
                             const webrtc_ice_candidate_t *candidate, 
                             void *userdata) {
    printf("ICE Candidate: %s\n", candidate->candidate);
}

static void on_data_channel(webrtc_peer_connection_t *pc, 
                           webrtc_data_channel_t *channel, 
                           void *userdata) {
    printf("Data Channel Created\n");
}

int main(void) {
    webrtc_init();
    
    // Configure ICE servers
    webrtc_config_t config = {0};
    const char *ice_servers[] = {"stun:stun.l.google.com:19302"};
    config.ice_servers = (char**)ice_servers;
    config.ice_server_count = 1;
    
    // Set up callbacks
    webrtc_callbacks_t callbacks = {
        .on_ice_candidate = on_ice_candidate,
        .on_data_channel = on_data_channel
    };
    
    // Create peer connection
    webrtc_peer_connection_t *pc = webrtc_create_peer_connection(
        &config, &callbacks, NULL);
    
    // Create data channel
    webrtc_data_channel_t *channel = webrtc_create_data_channel(pc, "test");
    
    // Create and set offer
    webrtc_session_description_t *offer;
    webrtc_create_offer(pc, &offer);
    webrtc_set_local_description(pc, offer);
    
    // Send data
    const char *msg = "Hello WebRTC!";
    webrtc_data_channel_send(channel, (const uint8_t*)msg, strlen(msg));
    
    // Cleanup
    webrtc_data_channel_close(channel);
    webrtc_destroy_peer_connection(pc);
    webrtc_cleanup();
    
    return 0;
}

Examples

Simple Example

./example_simple

DataChannel Example

./example_datachannel

Integration Test

./example_integration

API Overview

Initialization

• webrtc_init() - Initialize library
• webrtc_cleanup() - Cleanup resources

PeerConnection

• webrtc_create_peer_connection() - Create peer connection
• webrtc_destroy_peer_connection() - Destroy peer connection
• webrtc_create_offer() - Create SDP offer
• webrtc_create_answer() - Create SDP answer
• webrtc_set_local_description() - Set local SDP
• webrtc_set_remote_description() - Set remote SDP
• webrtc_add_ice_candidate() - Add ICE candidate

DataChannel

• webrtc_create_data_channel() - Create data channel
• webrtc_data_channel_send() - Send data
• webrtc_data_channel_close() - Close channel

ICE/STUN

• ice_agent_create() - Create ICE agent
• ice_agent_gather_candidates() - Gather candidates
• stun_send_request() - Send STUN binding request

SDP

• sdp_parse() - Parse SDP string
• sdp_generate() - Generate SDP string
• sdp_add_media() - Add media section

DTLS/SRTP

• dtls_context_create() - Create DTLS context
• dtls_generate_fingerprint() - Generate fingerprint
• srtp_protect() - Encrypt RTP packet
• srtp_unprotect() - Decrypt SRTP packet

SCTP

• sctp_context_create() - Create SCTP context
• sctp_send() - Send SCTP data
• sctp_receive() - Receive SCTP data

Platform Abstraction

The library abstracts platform-specific functionality:

• Threads: webrtc_thread_*
• Mutexes: webrtc_mutex_*
• Sockets: webrtc_socket_*
• Time: webrtc_time_ms(), webrtc_sleep_ms()
• Memory: webrtc_malloc(), webrtc_free()

Protocol Support

Protocol	Status	Description
ICE	✅ Implemented	Interactive Connectivity Establishment
STUN	✅ Implemented	Session Traversal Utilities for NAT
TURN	🚧 Partial	Traversal Using Relays around NAT
DTLS	✅ Implemented	Datagram Transport Layer Security
SRTP	✅ Implemented	Secure Real-time Transport Protocol
SCTP	✅ Implemented	Stream Control Transmission Protocol
SDP	✅ Implemented	Session Description Protocol

Roadmap

• Platform abstraction layer
• ICE/STUN implementation
• DTLS key exchange
• SRTP encryption
• SCTP data channels
• SDP parsing/generation
• Full TURN relay support
• OpenSSL/BoringSSL integration
• Media codec support (Opus, VP8, H.264)
• Bandwidth estimation
• Congestion control

License

MIT License - see LICENSE file for details.

Contributing

Contributions welcome! Please:

1. Follow the existing code style (C99)
2. Add tests for new features
3. Update documentation
4. Submit pull requests

References

• RFC 8445 - ICE
• RFC 5389 - STUN
• RFC 6347 - DTLS
• RFC 3711 - SRTP
• RFC 4960 - SCTP
• RFC 8866 - SDP