如何在tcp端口上使用二进制通信协议发送数据包
如何在tcp端口上使用二进制通信协议发送数据包
提问于 2017-04-25 18:21:15
我正在研制一种装置，它可以通过传感器测量一些读数。设备由Android应用程序操作。我必须从TCP层获取读数。这是在TCP上发送数据的代码。
TcpClient.java
import android.util.Log;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
/**
* Created by shahbaz on 25/4/17.
*/
public class TcpClient {
public static final String SERVER_IP = "192.168.1.76"; //server IP address
public static final int SERVER_PORT = 1800;
// message to send to the server
private String mServerMessage;
// sends message received notifications
private OnMessageReceived mMessageListener = null;
// while this is true, the server will continue running
private boolean mRun = false;
// used to send messages
private PrintWriter mBufferOut;
// used to read messages from the server
private BufferedReader mBufferIn;
/**
* Constructor of the class. OnMessagedReceived listens for the messages received from server
*/
public TcpClient(OnMessageReceived listener) {
mMessageListener = listener;
}
/**
* Sends the message entered by client to the server
*
* @param message text entered by client
*/
public void sendMessage(String message) {
if (mBufferOut != null && !mBufferOut.checkError()) {
mBufferOut.println(message);
mBufferOut.flush();
}
}
/**
* Close the connection and release the members
*/
public void stopClient() {
mRun = false;
if (mBufferOut != null) {
mBufferOut.flush();
mBufferOut.close();
}
mMessageListener = null;
mBufferIn = null;
mBufferOut = null;
mServerMessage = null;
}
public void run() {
mRun = true;
try {
//here you must put your computer's IP address.
InetAddress serverAddr = InetAddress.getByName(SERVER_IP);
Log.e("TCP Client", "C: Connecting...");
//create a socket to make the connection with the server
Socket socket = new Socket(serverAddr, SERVER_PORT);
try {
//sends the message to the server
mBufferOut = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);
//receives the message which the server sends back
mBufferIn = new BufferedReader(new InputStreamReader(socket.getInputStream()));
//in this while the client listens for the messages sent by the server
while (mRun) {
mServerMessage = mBufferIn.readLine();
if (mServerMessage != null && mMessageListener != null) {
//call the method messageReceived from MyActivity class
mMessageListener.messageReceived(mServerMessage);
}
}
Log.e("RESPONSE FROM SERVER", "S: Received Message: '" + mServerMessage + "'");
} catch (Exception e) {
Log.e("TCP", "S: Error", e);
} finally {
//the socket must be closed. It is not possible to reconnect to this socket
// after it is closed, which means a new socket instance has to be created.
socket.close();
}
} catch (Exception e) {
Log.e("TCP", "C: Error", e);
}
}
//Declare the interface. The method messageReceived(String message) will must be implemented in the MyActivity
//class at on asynckTask doInBackground
public interface OnMessageReceived {
public void messageReceived(String message);
}}
包结构
分组格式包含，在与TCP上的设备通信时，没有标识数据包之间的边界，在这种情况下，如果数据包不连续，或者如果有任何数据包丢失，就可以使用“报头开始”来识别新的数据包。因此，包中的前2个字节表示包的开始。
头开始:两个字节的字段，指示每个包的开始。0x55AA是一个2字节的数字，用作头开始。
协议版本:指定正在使用的协议版本的单字节字段.有效载荷中指定的版本将决定有效负载结构。在任何给定的时刻，设备将支持单一协议版本。目前的协议版本是‘1’。
DSN:序列号是1字节字段，它将唯一地标识数据包.数据包的请求者必须在请求有效负载中填充此字段；响应方必须在响应有效负载中填充相同的唯一标识符。
请求Id:单字节字段指定命令id。对有效负载的解析将根据命令id进行。在请求有效负载的情况下，该字段将为非零，如果响应为零，则为零。
有效载荷长度:双字节字段指定有效负载的长度(以字节为单位)。它指定了负载长度字段后面的字节数。在有效负载长度中，不包括报头长度和CRC。目前，网关设备支持的最大有效负载长度为512 (字节)。CRC: 1字节字段，它将由XORing计算所有字节，并添加XOR计数为0。
而且起作用了。但是根据docs协议，我必须使用二进制通信协议发送数据包。包括报头启动、有效载荷数据等。如何在数据包结构中发送这些params？如何创建数据包？
任何帮助都是非常感谢的。
回答 1
Stack Overflow用户
回答已采纳
发布于 2017-06-01 10:31:28
主要的错误是我没有过多考虑原始数据类型的大小。
字节=1字节
short =2字节
int =4字节
long =8字节
浮点数=4字节
double =8字节
char =2字节
在引用了原始数据类型的大小之后，我意识到我们应该跟踪数据包的大小和索引，因为我们处理的是字节数组。
TcpPacket.java
public class TcpPacket {
private static int header_start = 0x55AA;
private static int protocol_version = 1;
private PacketUtils packetUtils = new PacketUtils();
public byte[] getHandshakePacket()
{
int request_id = 1;
byte[] header_data = packetUtils.ItoBA2(header_start);
byte[] payload_data = packetUtils.ItoBA4(packetUtils.getDateTime());
byte[] payload_length = packetUtils.ItoBA2(4);
byte[] a_data = new byte[]{header_data[0], header_data[1], (byte) protocol_version, packetUtils.getDSN(), (byte) request_id, payload_length[0], payload_length[1],
payload_data[0], payload_data[1], payload_data[2], payload_data[3]};
byte[] b_data = new byte[]{ packetUtils.getCRC(a_data)};
byte[] packet_data = packetUtils.concatBytes(a_data,b_data);
return packet_data;
}
}PacketUtils.java
public class PacketUtils {
public byte[] ItoBA4(int value) { // integer to bytes function (return byte array of 4 bytes)
return new byte[] {
(byte)(value >>> 24),
(byte)(value >>> 16),
(byte)(value >>> 8),
(byte)value};
}
public byte[] ItoBA2(int value) { // integer to bytes function (return byte array of 2 bytes)
return new byte[] {
(byte)(value >>> 8),
(byte)value};
}
public byte getDSN() // return one byte random number
{
char[] chars = "1234567890".toCharArray();
StringBuilder sb = new StringBuilder();
Random random = new Random();
for (int i = 0; i < 1; i++) {
char c = chars[random.nextInt(chars.length)];
sb.append(c);
}
byte output = Byte.valueOf(sb.toString());
return output;
}
public byte getCRC(byte[] packet) // required CRC function (return byte)
{
try
{
if (packet == null)
{
//Logger.Error("empty packet received");
return (byte)0;
}
byte XORCheckSum = 0;
byte zeroCount = 0;
byte FFCount = 0;
for (int i = 0; i < packet.length; i++)
{
XORCheckSum ^= packet[i];
if (packet[i] == (byte) 0)
{
zeroCount++;
continue;
}
if (packet[i] == (byte)255)
{
FFCount++;
continue;
}
}
XORCheckSum ^= zeroCount;
XORCheckSum ^= FFCount;
return XORCheckSum;
}
catch (Exception ex)
{
//Logger.Error(ex);
return (byte)0;
}
}
byte[] concatBytes(byte[]...arrays) // concatenate byte arrays
{
// Determine the length of the result array
int totalLength = 0;
for (int i = 0; i < arrays.length; i++)
{
totalLength += arrays[i].length;
}
// create the result array
byte[] result = new byte[totalLength];
// copy the source arrays into the result array
int currentIndex = 0;
for (int i = 0; i < arrays.length; i++)
{
System.arraycopy(arrays[i], 0, result, currentIndex, arrays[i].length);
currentIndex += arrays[i].length;
}
return result;
}
public int getDateTime()
{
int dateInSec = (int) (System.currentTimeMillis() / 1000);
return dateInSec;
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/43618222
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