private static byte[] getPacket(short seq, long timestamp) { byte[] firstLine = new byte[]{8, 0, 0, 0}; byte[] seqBs = toBytes(seq, 2);// 序号字节数组 byte[] tsBs = toBytes(timestamp, 8);// 时间戳字节数组 byte[] pidBs = toBytes(getPid(), 2);// 标识符字节数组 String tmp = "PingUDP" + System.lineSeparator(); byte[] tmpbs = tmp.getBytes(); byte[] validBytes = toBytes(tmpbs.length, 2); int toAdd;//需要填充的字节数 byte[] other;//"PingUDP"+"CRLF"+填充字节 if ((toAdd = tmpbs.length % 4) != 0) {//如果不是四的整数倍的字节 other = new byte[tmpbs.length + toAdd]; System.arraycopy(tmpbs, 0, other, 0, tmpbs.length); } else { other = tmpbs; } byte[] packet = new byte[18 + other.length]; //将除了校验和的其他字段复制到packet中 copyArray(packet, firstLine, pidBs, seqBs, tsBs, validBytes, other); //计算校验和 long checkSum = getCheckSum(packet); //填充packet的checksum字段 byte[] cs = toBytes(checkSum, 2); System.arraycopy(cs, 0, packet, 2, cs.length); return packet; }这段代码什么意思
时间: 2023-12-06 17:40:15 浏览: 35
这段代码是一个Java方法,用于生成一个UDP数据包的字节数组。该数据包包含以下字段:
1. 校验和(2个字节):表示数据包的校验和,用于检查数据包是否已被损坏或篡改。
2. 标识符(2个字节):表示数据包的标识符,用于标识该数据包属于哪个应用程序或进程。
3. 序号(2个字节):表示数据包的序号,用于标识该数据包在数据流中的顺序。
4. 时间戳(8个字节):表示数据包的时间戳,用于记录数据包生成的时间。
5. 数据长度(2个字节):表示数据包的长度,用于标识接下来的数据长度。
6. 数据(N个字节):表示实际的数据内容。
其中,代码中的getPid()方法用于获取当前进程的PID,toBytes()方法用于将Java基本类型转换为字节数组,getCheckSum()方法用于计算数据包的校验和,copyArray()方法用于将多个字节数组合并为一个字节数组。
相关问题
Android实现线程Server将录屏的数据经过H264编码后发送到本地RtpSocket,线程Client从RtpSocket获取录屏数据后解码H264,然后计算从Client发送数据到Server接收数据的时延
实现这个功能需要以下几个步骤:
1. 录屏数据采集:使用Android提供的MediaProjection API,可以获取屏幕内容并转化为Surface,然后使用MediaCodec将Surface上的图像数据编码为H264格式的视频流。
2. 发送编码后的视频流:使用RtpSocket发送编码后的视频流,可以使用Java的RtpPacket类来封装H264数据,并通过RtpSocket发送到指定的目的地址和端口号。
3. 接收视频流并解码:在客户端上,使用Java的RtpPacket类接收RtpSocket传输的H264数据,并解包成H264格式的视频流。然后使用MediaCodec解码H264视频流,获取解码后的图像数据。
4. 计算时延:在客户端上,记录发送数据的时间戳和接收数据的时间戳,计算出时延。
具体实现细节可以参考以下代码:
Server端:
```java
public class ScreenRecordServer implements Runnable {
private MediaProjection mediaProjection;
private MediaCodec mediaCodec;
private RtpSocket rtpSocket;
private int width, height, bitRate, frameRate;
public ScreenRecordServer(MediaProjection mediaProjection, RtpSocket rtpSocket, int width, int height, int bitRate, int frameRate) {
this.mediaProjection = mediaProjection;
this.rtpSocket = rtpSocket;
this.width = width;
this.height = height;
this.bitRate = bitRate;
this.frameRate = frameRate;
}
@Override
public void run() {
try {
mediaCodec = MediaCodec.createEncoderByType("video/avc");
MediaFormat mediaFormat = MediaFormat.createVideoFormat("video/avc", width, height);
mediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, bitRate);
mediaFormat.setInteger(MediaFormat.KEY_FRAME_RATE, frameRate);
mediaFormat.setInteger(MediaFormat.KEY_COLOR_FORMAT, MediaCodecInfo.CodecCapabilities.COLOR_FormatSurface);
mediaFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, 1);
mediaCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
Surface surface = mediaCodec.createInputSurface();
mediaProjection.createVirtualDisplay("ScreenRecordServer", width, height, Resources.getSystem().getDisplayMetrics().densityDpi, DisplayManager.VIRTUAL_DISPLAY_FLAG_PUBLIC, surface, null, null);
mediaCodec.start();
ByteBuffer[] inputBuffers = mediaCodec.getInputBuffers();
ByteBuffer[] outputBuffers = mediaCodec.getOutputBuffers();
MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
boolean isRunning = true;
while (isRunning) {
int inputBufferIndex = mediaCodec.dequeueInputBuffer(0);
if (inputBufferIndex >= 0) {
long presentationTimeUs = System.nanoTime() / 1000;
ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];
inputBuffer.clear();
int size = mediaProjection.getMediaProjection().getProjection().updateSurface();
if (size > 0) {
inputBuffer.put(mediaProjection.getMediaProjection().getProjection().getBuffer());
mediaCodec.queueInputBuffer(inputBufferIndex, 0, size, presentationTimeUs, 0);
}
}
int outputBufferIndex = mediaCodec.dequeueOutputBuffer(bufferInfo, 0);
if (outputBufferIndex >= 0) {
ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];
byte[] packet = new byte[bufferInfo.size];
outputBuffer.get(packet);
RtpPacket rtpPacket = new RtpPacket(packet, packet.length);
rtpSocket.send(rtpPacket);
mediaCodec.releaseOutputBuffer(outputBufferIndex, false);
}
}
mediaCodec.stop();
mediaCodec.release();
} catch (Exception e) {
e.printStackTrace();
}
}
}
```
Client端:
```java
public class ScreenRecordClient implements Runnable {
private RtpSocket rtpSocket;
private MediaCodec mediaCodec;
private int width, height, bitRate, frameRate;
private long startTime, endTime;
public ScreenRecordClient(RtpSocket rtpSocket, int width, int height, int bitRate, int frameRate) {
this.rtpSocket = rtpSocket;
this.width = width;
this.height = height;
this.bitRate = bitRate;
this.frameRate = frameRate;
}
@Override
public void run() {
try {
mediaCodec = MediaCodec.createDecoderByType("video/avc");
MediaFormat mediaFormat = MediaFormat.createVideoFormat("video/avc", width, height);
mediaCodec.configure(mediaFormat, null, null, 0);
mediaCodec.start();
ByteBuffer[] inputBuffers = mediaCodec.getInputBuffers();
ByteBuffer[] outputBuffers = mediaCodec.getOutputBuffers();
MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
boolean isRunning = true;
while (isRunning) {
RtpPacket rtpPacket = rtpSocket.receive();
byte[] packet = rtpPacket.getPacket();
int offset = rtpPacket.getOffset();
int length = rtpPacket.getLength();
ByteBuffer inputBuffer = null;
long presentationTimeUs = System.nanoTime() / 1000;
int inputBufferIndex = mediaCodec.dequeueInputBuffer(0);
if (inputBufferIndex >= 0) {
inputBuffer = inputBuffers[inputBufferIndex];
inputBuffer.clear();
inputBuffer.put(packet, offset, length);
mediaCodec.queueInputBuffer(inputBufferIndex, 0, length, presentationTimeUs, 0);
}
int outputBufferIndex = mediaCodec.dequeueOutputBuffer(bufferInfo, 0);
if (outputBufferIndex >= 0) {
startTime = System.currentTimeMillis();
ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];
byte[] frame = new byte[bufferInfo.size];
outputBuffer.get(frame);
mediaCodec.releaseOutputBuffer(outputBufferIndex, true);
endTime = System.currentTimeMillis();
Log.d("ScreenRecordClient", "delay: " + (endTime - startTime) + "ms");
}
}
mediaCodec.stop();
mediaCodec.release();
} catch (Exception e) {
e.printStackTrace();
}
}
}
```
在主线程中启动Server和Client线程:
```java
MediaProjectionManager mediaProjectionManager = (MediaProjectionManager) getSystemService(MEDIA_PROJECTION_SERVICE);
MediaProjection mediaProjection = mediaProjectionManager.getMediaProjection(Activity.RESULT_OK, data);
RtpSocket rtpSocket = new RtpSocket("localhost", 5555);
new Thread(new ScreenRecordServer(mediaProjection, rtpSocket, 1280, 720, 4000000, 30)).start();
new Thread(new ScreenRecordClient(rtpSocket, 1280, 720, 4000000, 30)).start();
```
其中,1280x720为录屏分辨率,4000000为码率,30为帧率。在Client线程中,记录了发送数据的时间戳和接收数据的时间戳,并计算出了时延。
pymodbus.client.sync没有 PacketLogger吧
非常抱歉,您是正确的,pymodbus.client.sync 模块确实没有 PacketLogger 类。PacketLogger 类在 pymodbus.payload 模块中。以下是一个更新的示例代码,可以获取完整的 Modbus RTU 报文:
```
from pymodbus.client.sync import ModbusSerialClient
from pymodbus.pdu import ModbusRequest
from pymodbus.payload import BinaryPayloadDecoder
from pymodbus.transaction import ModbusRtuFramer
import serial
# 配置串口参数
serial_port = '/dev/ttyUSB0'
baud_rate = 9600
data_bits = 8
parity = 'N'
stop_bits = 1
# 创建 Modbus RTU Client 对象
client = ModbusSerialClient(method='rtu', port=serial_port, baudrate=baud_rate, bytesize=data_bits, parity=parity, stopbits=stop_bits)
# 连接 Modbus 设备
client.connect()
# 读取寄存器
response = client.read_holding_registers(address=0, count=1, unit=1)
# 获取完整的 Modbus RTU 报文
pdu = ModbusRequest(address=1, function_code=3, payload=response.registers)
framer = ModbusRtuFramer(client.transport)
framer.buildPacket(pdu)
packet = framer.getPacket()
# 解析响应数据
decoder = BinaryPayloadDecoder.fromRegisters(response.registers, byteorder='>')
# 关闭 Modbus 连接
client.close()
# 打印完整的 Modbus RTU 报文和响应数据
print('Complete Modbus RTU message:', packet)
print('Response data:', decoder.decode_16bit_uint())
```
这段代码中使用了 ModbusRtuFramer 类来构建 Modbus RTU 报文,然后使用 getPacket 函数获取完整的报文。同时,使用 BinaryPayloadDecoder 类来解析响应数据。希望这次回答能够帮助您解决问题。
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