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[英]Sending data over sockets in Java and receiving in C++ with QT sockets
[英]Java sending and receiving file (byte[]) over sockets
我正在尝试开发一个非常简单的客户端/服务器,其中客户端将文件转换为字节,将其发送到服务器,然后将字节转换回文件。
目前该程序只创建一个空文件。 我不是一个出色的 Java 开发人员,因此非常感谢任何帮助。
这是接收客户端发送的内容的服务器部分。
ServerSocket serverSocket = null;
serverSocket = new ServerSocket(4444);
Socket socket = null;
socket = serverSocket.accept();
DataOutputStream out = new DataOutputStream(new BufferedOutputStream(socket.getOutputStream()));
DataInputStream in = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
byte[] bytes = new byte[1024];
in.read(bytes);
System.out.println(bytes);
FileOutputStream fos = new FileOutputStream("C:\\test2.xml");
fos.write(bytes);
这是客户端部分
Socket socket = null;
DataOutputStream out = null;
DataInputStream in = null;
String host = "127.0.0.1";
socket = new Socket(host, 4444);
out = new DataOutputStream(new BufferedOutputStream(socket.getOutputStream()));
in = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
File file = new File("C:\\test.xml");
//InputStream is = new FileInputStream(file);
// Get the size of the file
long length = file.length();
if (length > Integer.MAX_VALUE) {
System.out.println("File is too large.");
}
byte[] bytes = new byte[(int) length];
//out.write(bytes);
System.out.println(bytes);
out.close();
in.close();
socket.close();
在 Java 中复制流的正确方法如下:
int count;
byte[] buffer = new byte[8192]; // or 4096, or more
while ((count = in.read(buffer)) > 0)
{
out.write(buffer, 0, count);
}
希望每次我在论坛上发帖时都能得到一美元。
谢谢您的帮助。 我现在已经设法让它工作了,所以我想我会发布以便其他人可以用来帮助他们。
服务器:
public class Server {
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(4444);
} catch (IOException ex) {
System.out.println("Can't setup server on this port number. ");
}
Socket socket = null;
InputStream in = null;
OutputStream out = null;
try {
socket = serverSocket.accept();
} catch (IOException ex) {
System.out.println("Can't accept client connection. ");
}
try {
in = socket.getInputStream();
} catch (IOException ex) {
System.out.println("Can't get socket input stream. ");
}
try {
out = new FileOutputStream("M:\\test2.xml");
} catch (FileNotFoundException ex) {
System.out.println("File not found. ");
}
byte[] bytes = new byte[16*1024];
int count;
while ((count = in.read(bytes)) > 0) {
out.write(bytes, 0, count);
}
out.close();
in.close();
socket.close();
serverSocket.close();
}
}
和客户:
public class Client {
public static void main(String[] args) throws IOException {
Socket socket = null;
String host = "127.0.0.1";
socket = new Socket(host, 4444);
File file = new File("M:\\test.xml");
// Get the size of the file
long length = file.length();
byte[] bytes = new byte[16 * 1024];
InputStream in = new FileInputStream(file);
OutputStream out = socket.getOutputStream();
int count;
while ((count = in.read(bytes)) > 0) {
out.write(bytes, 0, count);
}
out.close();
in.close();
socket.close();
}
}
这是服务器打开文件流并通过网络发送
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class SimpleFileServer {
public final static int SOCKET_PORT = 5501;
public final static String FILE_TO_SEND = "file.txt";
public static void main (String [] args ) throws IOException {
FileInputStream fis = null;
BufferedInputStream bis = null;
OutputStream os = null;
ServerSocket servsock = null;
Socket sock = null;
try {
servsock = new ServerSocket(SOCKET_PORT);
while (true) {
System.out.println("Waiting...");
try {
sock = servsock.accept();
System.out.println("Accepted connection : " + sock);
// send file
File myFile = new File (FILE_TO_SEND);
byte [] mybytearray = new byte [(int)myFile.length()];
fis = new FileInputStream(myFile);
bis = new BufferedInputStream(fis);
bis.read(mybytearray,0,mybytearray.length);
os = sock.getOutputStream();
System.out.println("Sending " + FILE_TO_SEND + "(" + mybytearray.length + " bytes)");
os.write(mybytearray,0,mybytearray.length);
os.flush();
System.out.println("Done.");
} catch (IOException ex) {
System.out.println(ex.getMessage()+": An Inbound Connection Was Not Resolved");
}
}finally {
if (bis != null) bis.close();
if (os != null) os.close();
if (sock!=null) sock.close();
}
}
}
finally {
if (servsock != null)
servsock.close();
}
}
}
这是客户端接收通过网络发送的文件
import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.Socket;
public class SimpleFileClient {
public final static int SOCKET_PORT = 5501;
public final static String SERVER = "127.0.0.1";
public final static String
FILE_TO_RECEIVED = "file-rec.txt";
public final static int FILE_SIZE = Integer.MAX_VALUE;
public static void main (String [] args ) throws IOException {
int bytesRead;
int current = 0;
FileOutputStream fos = null;
BufferedOutputStream bos = null;
Socket sock = null;
try {
sock = new Socket(SERVER, SOCKET_PORT);
System.out.println("Connecting...");
// receive file
byte [] mybytearray = new byte [FILE_SIZE];
InputStream is = sock.getInputStream();
fos = new FileOutputStream(FILE_TO_RECEIVED);
bos = new BufferedOutputStream(fos);
bytesRead = is.read(mybytearray,0,mybytearray.length);
current = bytesRead;
do {
bytesRead =
is.read(mybytearray, current, (mybytearray.length-current));
if(bytesRead >= 0) current += bytesRead;
} while(bytesRead > -1);
bos.write(mybytearray, 0 , current);
bos.flush();
System.out.println("File " + FILE_TO_RECEIVED
+ " downloaded (" + current + " bytes read)");
}
finally {
if (fos != null) fos.close();
if (bos != null) bos.close();
if (sock != null) sock.close();
}
}
}
避免文件大小的限制,在创建文件大小byte[] bytes = new byte[(int) length];
的数组时,会导致抛出异常java.lang.OutOfMemoryError
byte[] bytes = new byte[(int) length];
,相反我们可以做
byte[] bytearray = new byte[1024*16];
FileInputStream fis = null;
try {
fis = new FileInputStream(file);
OutputStream output= socket.getOututStream();
BufferedInputStream bis = new BufferedInputStream(fis);
int readLength = -1;
while ((readLength = bis.read(bytearray)) > 0) {
output.write(bytearray, 0, readLength);
}
bis.close();
output.close();
}
catch(Exception ex ){
ex.printStackTrace();
} //Excuse the poor exception handling...
菜鸟,如果想通过socket写文件到服务器,用fileoutputstream代替dataoutputstream怎么样? dataoutputstream 更适合协议级读写。 以字节为单位的代码读写不是很合理。 java io中需要循环读写。 而且,您使用缓冲方式。 冲洗是必要的。 这是一个代码示例: http : //www.rgagnon.com/javadetails/java-0542.html
加上 EJP 的回答; 使用它以获得更多的流动性。 确保你没有把他的代码放在一个更大的 try catch 中,在 .read 和 catch 块之间有更多的代码,它可能会返回一个异常并一直跳到外部的 catch 块,最安全的做法是放置 EJPS 的 while 循环在 try catch 中,然后在它之后继续代码,例如:
int count;
byte[] bytes = new byte[4096];
try {
while ((count = is.read(bytes)) > 0) {
System.out.println(count);
bos.write(bytes, 0, count);
}
} catch ( Exception e )
{
//It will land here....
}
// Then continue from here
编辑:^这发生在我身上,因为我没有意识到如果它是客户端到服务器的流,你需要放置 socket.shutDownOutput() !
希望这篇文章能解决你的任何问题
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