我编写了一个多客户端TCP服务器，它具有发送Json（基于文本）命令字符串以及向多个客户端发送SQLite数据库文件的双重目的。一切都很好，除了...数据库文件使用特殊字符hex81（十进制129）用于某些内部目的。当我将数据库文件读入字节数组时，由于Java的带符号字节表示，Java会将此字符转换为十进制-127。但是套接字实际上是将此字符作为hex3F传输。因此，当我收到客户端中的数据保存并将其保存到文件时，由于存在h3F字符而不是h81，数据库已损坏。
为什么会发生这种情况，我该如何纠正？
以下是我用于服务器的完整代码（无论何时客户端连接，此类的新实例都由单独的TCPServer类启动）：
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答案 0 :(得分：-1)
正如EJP建议的那样，问题在于使用读者和作者。 以下代码现在按预期工作（感谢提示EJP）。我将解决VGR引发的关于在PrintWriter和BufferedOutputStream中包装client.getOutputStream（）的问题，但是现在代码运行良好（这是一项正在进行的工作）。
public class TCPServerThread extends Thread {
// Connect status constants
private final static int NULL = 0;
private final static int DISCONNECTED = 1;
private final static int DISCONNECTING = 2;
private final static int BEGIN_CONNECT = 3;
private final static int CONNECTED = 4;
private final static String END_SESSION = new Character((char)0).toString(); // Indicates the end of a session
// Connection state info
private int connectionStatus = DISCONNECTED;
private static StringBuffer txBuffer = new StringBuffer("");
private static BufferedOutputStream out2 = null;
private static File file;
// TCP Components
private ServerSocket serverSocket = null;
private Socket clientSocket = null;
private BufferedReader in = null;
private PrintWriter out = null;
private static BufferedInputStream fileData = null;
private String s = "";
private DecodeJson dj = new DecodeJson();
private boolean doRun;
public TCPServerThread(Socket socket) throws IOException {
doRun = true;
clientSocket = socket;
changeStatusTS(BEGIN_CONNECT, true);
}
public void run() {
while (doRun) {
try { // run every ~10 ms
Thread.sleep(10);
}
catch (InterruptedException e) {}
if (Mainscreen.shutdown == true || TCPClient.close == true)
connectionStatus = DISCONNECTING;
switch (connectionStatus) {
case BEGIN_CONNECT:
try {
in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
out = new PrintWriter(clientSocket.getOutputStream(), true);
out2 = new BufferedOutputStream(clientSocket.getOutputStream());
TCPServer.writers.add(out); // add this socket to the connected clients list
changeStatusTS(CONNECTED, true);
}
// If error, clean up and output an error message
catch (IOException e) {
cleanUp();
changeStatusTS(DISCONNECTED, false);
}
break;
case CONNECTED:
try {
// Send data
if (txBuffer.length() != 0) {
for (PrintWriter writer : TCPServer.writers) {
writer.print(txBuffer);
writer.flush();
if(writer.checkError()) {
closeSocket();
changeStatusTS(DISCONNECTING, true);
}else {
changeStatusTS(NULL, true);
}
}
txBuffer.setLength(0);
}
if (fileData != null) {
byte[] buffer = new byte[(int) file.length()];
for (int read = fileData.read(buffer); read >=0; read = fileData.read(buffer)) out2.write(buffer, 0, read);
out2.flush();
fileData = null;
}
// Receive data
if (in.ready()) {
s = in.readLine();
if ((s != null) && (s.length() != 0)) {
// Check if it is the end of a transmission
if (s.equals(END_SESSION)) {
changeStatusTS(DISCONNECTING, true);
}
// Otherwise, receive text
else {
dj.receiveString(s);
changeStatusTS(NULL, true);
}
}
}
}
catch (IOException e) {
System.out.println("Socket error " + e);
cleanUp();
changeStatusTS(DISCONNECTED, false);
}
break;
case DISCONNECTING:
// Tell clients to disconnect as well
if (out != null) {
out.print(END_SESSION);
out.flush();
}
// Clean up (close all streams/sockets)
cleanUp();
changeStatusTS(DISCONNECTED, true);
break;
default: break;
}
}
}
// Add command to text send-buffer
public static void sendString(String s) {
synchronized (txBuffer) {
txBuffer.append(s + "\n");
}
}
// Add file data to binary send buffer
public static void sendFile(String filename) {
file = new File(filename);
try {
fileData = new BufferedInputStream(new FileInputStream(file));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
private void changeStatusTS(int newConnectStatus, boolean noError) {
// Change state if valid state
if (newConnectStatus != NULL) {
connectionStatus = newConnectStatus;
}
}
private void closeSocket(){
try {
if (clientSocket != null) {
clientSocket.close();
clientSocket = null;
}
}
catch (IOException e) { clientSocket = null; }
}
// Cleanup for disconnect
private void cleanUp() {
try {
if (serverSocket != null) {
serverSocket.close();
serverSocket = null;
}
}
catch (IOException e) { serverSocket = null; }
try {
if (clientSocket != null) {
clientSocket.close();
clientSocket = null;
}
}
catch (IOException e) { clientSocket = null; }
try {
if (in != null) {
in.close();
in = null;
}
}
catch (IOException e) { in = null; }
if (out != null) {
TCPServer.writers.remove(out); // remove this socket for the connected sockets list
out.close();
out = null;
}
doRun = false;
}
}