如何用websocket+webRtc后端实现视频通话

<dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-websocket</artifactId>
        </dependency>

@Data
public class WebRTCSignalingMessage extends IMCommand {

    private String type;// 消息类型

    private Object offer;  // offer内容

    private Object iceCandidate; // iceCandidate信息

    private Object answer; // answer数据

    private String fromUserId; //用户id

    private String targetUserId; // 目标用户ID


}

public class RtpPacketDecoder extends ReplayingDecoder<Void> {

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        int header = in.readUnsignedByte();
        int version = (header >> 6) & 0x3;
        int padding = (header >> 5) & 0x1;
        int extension = (header >> 4) & 0x1;
        int cc = header & 0xf;

        header = in.readUnsignedByte();
        int marker = (header >> 7) & 0x1;
        int payloadType = header & 0x7f;

        int sequenceNumber = in.readUnsignedShort();
        int timestamp = in.readInt();
        int ssrc = in.readInt();

        int payloadLength = in.readableBytes();
        byte[] payload = new byte[payloadLength];
        in.readBytes(payload);

        out.add(new RtpPacket(version, padding, extension, cc, marker, payloadType, sequenceNumber, timestamp, ssrc, payload));
    }
}

// RTP数据包编码器
public class RtpPacketEncoder extends MessageToByteEncoder<RtpPacket> {
    /**
     * 编码方法，将RtpPacket对象编码为字节流
     *
     * @param ctx           上下文对象，包含通道信息
     * @param packet        待编码的RtpPacket对象
     * @param out           ByteBuf对象，用于存储编码后的字节流
     * @throws Exception    编码过程中可能抛出的异常
     */
    @Override
    protected void encode(ChannelHandlerContext ctx, RtpPacket packet, ByteBuf out) throws Exception {
        // 构造RTP头的第一个字节
        byte header = (byte) ((packet.getVersion() << 6) | (packet.getPadding() << 5) |
                (packet.getExtension() << 4) | packet.getCc());
        out.writeByte(header);

        // 构造RTP头的第二个字节
        header = (byte) ((packet.getMarker() << 7) | packet.getPayloadType());
        out.writeByte(header);

        // 写入序列号
        out.writeShort(packet.getSequenceNumber());
        // 写入时间戳
        out.writeInt(packet.getTimestamp());
        // 写入SSRC
        out.writeInt(packet.getSsrc());

        // 如果有效载荷不为空，则写入有效载荷
        if (packet.getPayload()!= null) {
            out.writeBytes(packet.getPayload());
        }
    }
}

@Slf4j
public class MediaStreamForwarder extends SimpleChannelInboundHandler<RtpPacket> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, RtpPacket packet) throws Exception {
        // 这里简单地将RTP数据包转发给所有其他客户端，实际应用中需要更智能的转发逻辑
        for (ChannelHandlerContext targetCtx : IMServer.USERS.values()) {
            if (targetCtx!= ctx) {
                targetCtx.writeAndFlush(packet);
            }
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        log.error("Media stream forwarding error", cause);
        ctx.close();
    }
}