Java DatagramSocket将随机停止接收数据包(有时仍会接收)
我正在尝试用Java实现一个TFTP客户机。客户端可以在本地主机上完美地工作,有时还可以通过网络发送到TFTP服务器。然而,有时我的DatagramSocket会随机停止接收数据包。它将发送读/写请求,但从未收到服务器试图发回的下一条消息。我已经检查了Wireshark,服务器肯定正在接收并尝试发送。在需要的地方关闭防火墙。我想不出是什么问题。以下是我正在使用的代码:Java DatagramSocket将随机停止接收数据包(有时仍会接收),java,sockets,udp,datagram,tftp,Java,Sockets,Udp,Datagram,Tftp,我正在尝试用Java实现一个TFTP客户机。客户端可以在本地主机上完美地工作,有时还可以通过网络发送到TFTP服务器。然而,有时我的DatagramSocket会随机停止接收数据包。它将发送读/写请求,但从未收到服务器试图发回的下一条消息。我已经检查了Wireshark,服务器肯定正在接收并尝试发送。在需要的地方关闭防火墙。我想不出是什么问题。以下是我正在使用的代码: public class TFTPClient { String filename; String mode; boolean
public class TFTPClient {
String filename;
String mode;
boolean read;
PacketBuilder builder;
String IP;
JFrame frame;
public TFTPClient(String uifilename, String uimode, boolean uiread, String uiIP, JFrame uiFrame){
this.filename = uifilename;
this.read = uiread;
this.mode = uimode;
this.IP = uiIP;
builder = new PacketBuilder();
this.frame = uiFrame;
}
/*
* Method choses between reading a file and writing a file based on boolean selected in main UI.
*/
public void startTFTP() throws IOException{
if (read){
readFile();
}
else{
writeFile();
}
}
/*
* Method is used for writing a file
*/
private void writeFile() throws IOException{
byte[] WRQ = builder.getWRQ(filename,mode);
String filenameAndExtension = filename;
RandomAccessFile f = new RandomAccessFile(filenameAndExtension, "r");
byte[] fileBytes = new byte[(int)f.length()];
f.read(fileBytes);
f.close();
DatagramSocket TFTPSocket = new DatagramSocket();
TFTPSocket.setSoTimeout(5000);
//create the packet and send to port 69 of the given IP
DatagramPacket wrqPacket = new DatagramPacket(WRQ, WRQ.length,
InetAddress.getByName(IP), 69);
try {
TFTPSocket.send(wrqPacket);
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
byte[] ackByte = new byte[4];
DatagramPacket ackPacket = new DatagramPacket(ackByte,
ackByte.length);
int blockNumber = 0;
DatagramPacket dataPacket;
boolean terminateOnNextAck = false;
boolean needExtraDataPacket = false;
int currentIndex = 0;
while(true)
{
TFTPSocket.receive(ackPacket);
System.out.println("Server acked " + ackByte[3]);
System.out.println("Expected ack " + blockNumber);
blockNumber++;
if(terminateOnNextAck){
break;
}
byte[]DATAdata;
if (needExtraDataPacket){
DATAdata = new byte[0];
terminateOnNextAck = true;
}
else if (currentIndex + 512 > fileBytes.length){
//This is our last byte. Length will be smaller than 508
DATAdata = new byte [fileBytes.length - currentIndex];
terminateOnNextAck = true;
}
else{
DATAdata = new byte[512];
}
if (currentIndex + 512 ==fileBytes.length){
needExtraDataPacket = true;
}
for (int i = 0; i<DATAdata.length; i++){
DATAdata[i] = fileBytes[currentIndex];
currentIndex++;
}
byte[] DATA = builder.getData(DATAdata, blockNumber);
dataPacket = new DatagramPacket(DATA, DATA.length,
InetAddress.getByName(IP),ackPacket.getPort());
try {
TFTPSocket.send(dataPacket);
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
}
TFTPSocket.close();
System.out.println("Write sucessful");
}
/*
* Method is used for reading a file
*/
private void readFile() throws IOException{
//Get RRQ packet
byte[] RRQ = builder.getRRQ(filename,mode);
StringBuffer fileText = new StringBuffer();
DatagramSocket TFTPSocket = new DatagramSocket();
TFTPSocket.setSoTimeout(5000);
//create the packet and send to port 69 of the given IP
DatagramPacket rrqPacket = new DatagramPacket(RRQ, RRQ.length,
InetAddress.getByName(IP), 69);
try {
TFTPSocket.send(rrqPacket);
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
byte[] dataByte = new byte[516];
for (int i = 516;i<516;i++){
dataByte[i] = 0;
}
DatagramPacket dataPacket = new DatagramPacket(dataByte,
dataByte.length);
System.out.println("Client: Waiting for packet.");
DatagramPacket ackPacket;
boolean error = false;
while(true)
{
TFTPSocket.receive(dataPacket);
System.out.println(TFTPSocket.getLocalPort());
if (dataByte[1] == 5){
error = true;
break;
}
fileText.append(new String(dataPacket.getData(),0,dataPacket.getLength()));
byte blockNumbers[] = new byte[2];
blockNumbers[0] = dataByte[2];
blockNumbers[1] = dataByte[3];
byte[] ACK = builder.getACK(blockNumbers);
ackPacket = new DatagramPacket(ACK, ACK.length,
InetAddress.getByName(IP),dataPacket.getPort());
try {
TFTPSocket.send(ackPacket);
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
if (dataByte[515] == 0){
break;
}
dataByte[515] = 0;
}
if (!error){
JOptionPane.showMessageDialog(frame, "Read Successful!");
System.out.println(fileText);
}
else{
JOptionPane.showMessageDialog(frame,"Error from server: " + new String(dataPacket.getData(),0,dataPacket.getLength()));
}
}
}
公共类TFTPClient{
字符串文件名;
字符串模式;
布尔读取;
包装制造商;
字符串IP;
JFrame框架;
公共TFTPClient(字符串uifilename、字符串uimode、布尔uiread、字符串uiIP、JFrame uiFrame){
this.filename=uifilename;
this.read=uiread;
this.mode=uimode;
this.IP=uiIP;
builder=新的PacketBuilder();
this.frame=uiFrame;
}
/*
*方法根据主UI中选择的布尔值在读取文件和写入文件之间进行选择。
*/
public void startTFTP()引发IOException{
如果(读){
readFile();
}
否则{
writeFile();
}
}
/*
*方法用于写入文件
*/
私有void writeFile()引发IOException{
字节[]WRQ=builder.getWRQ(文件名,模式);
字符串filename和extension=filename;
RandomAccessFile f=新的RandomAccessFile(文件名和扩展,“r”);
byte[]fileBytes=新字节[(int)f.length()];
f、 读取(文件字节);
f、 close();
DatagramSocket TFTPSocket=新的DatagramSocket();
TFTPSocket.setosotimeout(5000);
//创建数据包并发送到给定IP的端口69
DatagramPacket wrqPacket=新的DatagramPacket(WRQ,WRQ.length,
InetAddress.getByName(IP),69);
试一试{
TFTPSocket.send(wrqPacket);
}捕获(IOE异常){
e、 printStackTrace();
系统出口(1);
}
字节[]ackByte=新字节[4];
DatagramPacket ackPacket=新的DatagramPacket(ackByte,
ackByte.length);
int blockNumber=0;
数据包;
布尔terminateOnNextAck=false;
布尔值needExtraDataPacket=false;
int currentIndex=0;
while(true)
{
TFTPSocket.receive(ackPacket);
System.out.println(“服务器已确认”+ackByte[3]);
System.out.println(“预期确认”+区块编号);
blockNumber++;
如果(terminateOnNextAck){
打破
}
字节[]数据数据;
如果(需要外部数据包){
DATAdata=新字节[0];
terminateOnNextAck=true;
}
else if(currentIndex+512>fileBytes.length){
//这是最后一个字节。长度将小于508
DATAdata=新字节[fileBytes.length-currentIndex];
terminateOnNextAck=true;
}
否则{
DATAdata=新字节[512];
}
if(currentIndex+512==fileBytes.length){
needExtraDataPacket=true;
}
对于(int i=0;i这个问题原来是Mac OS X的问题。该程序在Windows上运行良好。但不完全确定原因。这个stackoverflow看到了类似的问题。Java UDP堆栈有问题吗?还可以看看下面的stackoverflow帖子:@RichardChambers没有“Java UDP堆栈”。Java只是提供了一个C sockets API上的n层。UDP堆栈在内核中。你找到过这个问题的答案吗?目前我在macOS/Java上观察到一个UDP问题,没有找到太多关于它的内容。。。