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Java BufferedReader frozen [duplicate]

I wanna write the code to let Client send a string to Server, Server print the string and reply a string, then Client print the string Server reply.
My Server
public class Server {
public static void main(String[] args) throws IOException {
ServerSocket ss = null;
Socket s = null;
try {
ss = new ServerSocket(34000);
s = ss.accept();
BufferedReader in = new BufferedReader(new InputStreamReader(
s.getInputStream()));
OutputStreamWriter out = new OutputStreamWriter(s.getOutputStream());
while (true) {
String string = in.readLine();
if (string != null) {
System.out.println("br: " + string);
if (string.equals("end")) {
out.write("to end");
out.flush();
out.close();
System.out.println("end");
// break;
}
}
}
} catch (IOException e) {
e.printStackTrace();
} finally {
s.close();
ss.close();
}
}
}
My Client:
public class Client {
public static void main(String[] args) {
Socket socket =null;
try {
socket = new Socket("localhost", 34000);
BufferedReader in =new BufferedReader(new InputStreamReader(socket.getInputStream()));
OutputStreamWriter out = new OutputStreamWriter(socket.getOutputStream());
String string = "";
string = "end";
out.write(string);
out.flush();
while(true){
String string2 = in.readLine();
if(string2.equals("to end")){
System.out.println("yes sir");
break;
}
}
} catch (Exception e) {
e.printStackTrace();
}finally{
try {
System.out.println("closed client");
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
are there some somethings wrong? if i remove the code "while(true) ..." in client class, it's OK.

you should add "\r\n" at the end of the String which write into stream.
example:
client :
string = "end";
out.write(string + "\r\n");
out.flush();
server :
out.write("to end" + "\r\n");
out.flush();
out.close();
System.out.println("end");
// break;

I don't see the server response.
You do a
System.out.println("br: " + string);
but not a
out.write(string);
out.flush();

Appand "\n" to end of the response from server.
outToClient.writeBytes(sb.toString() + "\n");

You are reading lines but you aren't writing lines. Add a newline, or call BufferedReader.newLine().

Socket client blocks forever

I'm coding socket client in Java.
In the program, I want to get information from server.
When the server receives "GET_LIGHTS" command, it sends back data in JSON format.
But in my code, bw.write() and bw.flush() doesn't work before socket.close().
So, the BufferedReader object is not ready: br.ready() returns false.
Is there any mistake in my code?
The client code is shown bellow.
package monitor;
import java.io.*;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.util.ArrayList;
public class SocketClient {
static private int port;
static private String hostName;
private Socket socket;
public SocketClient(String host, int port) {
this.hostName = host;
this.port = port;
}
// get lights by JSON
public void getLights() {
try {
// generate socket
InetSocketAddress endpoint = new InetSocketAddress(hostName, port);
socket = new Socket();
socket.connect(endpoint);
// setting
OutputStreamWriter out = new OutputStreamWriter(socket.getOutputStream());
BufferedWriter bw = new BufferedWriter(out);
InputStreamReader in = new InputStreamReader(socket.getInputStream());
BufferedReader br = new BufferedReader(in);
// send command
bw.write("GET_LIGHTS");
bw.flush();
// receive message from server
System.out.println(br.readLine());
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
public void initLights(ArrayList<Light> lights) {
getLights();
}
}
Edited:
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
public class SocketServer extends Thread{
static final int PORT = 44344;
static private ILS ils;
private ServerSocket serverSocket;
private Socket socket;
public SocketServer(ILS ils) {
this.ils = ils;
}
#Override
public void run() {
serverSocket = null;
System.out.println("Server: listening");
try {
serverSocket = new ServerSocket(PORT);
while(true){
socket = serverSocket.accept();
BufferedReader br = new BufferedReader(
new InputStreamReader(socket.getInputStream()));
ArrayList<String> cmd = new ArrayList<>();
String in;
while( (in = br.readLine()) != null ){
cmd.add(in);
}
command(cmd);
if( socket != null){
socket.close();
}
}
} catch (IOException e) {
e.printStackTrace();
}
if( serverSocket != null){
try {
serverSocket.close();
serverSocket = null;
} catch (IOException e) {
e.printStackTrace();
}
}
}
// send message to client
private void sendMessage(String str) {
System.out.println(str);
try {
OutputStream output = socket.getOutputStream();
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(output));
bw.write(str + "¥n");
bw.flush();
bw.close();
} catch (IOException e) {
e.printStackTrace();
}
}
// error
private void printError(String err) {
String str = "ERROR; ";
str += err;
sendMessage(str);
}
public void command(ArrayList<String> cmd) {
String mode = cmd.get(0);
if(mode == null){
}else switch(mode){
case "MANUAL_SIG-ALL":
System.out.println("全照明一括 信号値指定調光");
manualSigAll(cmd.get(1));
break;
case "MANUAL_SIG-INDIVIDUAL":
System.out.println("全照明独立 信号値指定調光");
manualSigIndividual(cmd.get(1));
break;
case "MANUAL_ID-SIG":
System.out.println("照明ID・信号値指定調光");
manualIDSig(cmd.get(1));
break;
case "MANUAL_ID-RELATIVE":
System.out.println("照明ID・相対信号値指定調光");
break;
case "DOWNLIGHT_ALL":
System.out.println("Downlight: All Control");
downlightAll(cmd.get(1));
break;
case "DOWNLIGHT_INDIVIDUAL":
System.out.println("Downlight: Individual control");
downlightIndividual(cmd.get(1));
break;
case "GET_LIGHTS":
System.out.println("Sending lights via JSON");
sendLights();
break;
default:
System.out.println("Error: 不明なmode command");
}
}
// 全照明一括 信号値指定調光
private void manualSigAll(String sigs) {
if(sigs == null) {
System.out.println("信号値のフォーマットを確認してください");
} else {
ArrayList<Integer> s = new ArrayList<>();
String[] buf = sigs.split(",");
for(String i:buf) s.add(Integer.parseInt(i));
for(Light l: ils.getLights()) {
l.setLumPct((double)s.get(0)/255.0*100.0);
l.setSignal(s.get(0), s.get(1));
}
}
// 調光
ils.downlightDimmer.send();
}
// 全照明独立 信号値指定調光
private void manualSigIndividual(String sigs) {
if(sigs == null) {
System.out.println("信号値のフォーマットを確認してください");
} else {
ArrayList<Integer> s = new ArrayList<>();
String[] buf = sigs.split(",");
for(String i:buf) s.add(Integer.parseInt(i));
for(int i=0; i<ils.getLights().size(); i++) {
ils.getLights().get(i).setSignal(s.get(0), s.get(1));
s.remove(0);
s.remove(0);
}
}
ils.downlightDimmer.send();
}
// 照明ID・信号値指定調光
private void manualIDSig(String sigs) {
if(sigs == null) {
System.out.println("信号値のフォーマットを確認してください");
} else {
ArrayList<Integer> s = new ArrayList<>();
String[] buf = sigs.split(",");
for(String i:buf) s.add(Integer.parseInt(i));
System.out.println(s.get(0));
ils.getLight(s.get(0)).setSignal(s.get(1), s.get(2));
}
ils.downlightDimmer.send();
}
private void downlightAll(String cmd) {
if(cmd == null) {
printError("Check for data command.");
} else {
ArrayList<Double> data = new ArrayList<>();
String[] buf = cmd.split(",");
for(String i:buf) data.add(Double.parseDouble(i));
for(Light l: ils.getLights()) {
l.setLumPct(data.get(0));
l.setTemperature(data.get(1));
}
}
// dimming
ils.downlightDimmer.send();
}
private void downlightIndividual(String cmd) {
if(cmd == null) {
printError("Check for data command.");
} else {
ArrayList<Integer> id = new ArrayList<>();
ArrayList<Double> lumPct = new ArrayList<>();
ArrayList<Integer> temp = new ArrayList<>();
String[] buf = cmd.split(",");
if(buf.length % 3 != 0) {printError("invalid number of data.");}
for(int i=0; i<buf.length/3; i++) {
int n = i*3;
try {
id.add(Integer.parseInt(buf[n]));
lumPct.add(Double.parseDouble(buf[n + 1]));
temp.add(Integer.parseInt(buf[n + 2]));
} catch (Exception e) {
printError(e.getMessage());
return;
}
}
while (id.size() > 0) {
// update light object
Light light = ils.getLight(id.get(0));
light.setLumPct(lumPct.get(0));
light.setTemperature(temp.get(0));
// remove data from array list
id.remove(0);
lumPct.remove(0);
temp.remove(0);
}
// dimming
ils.downlightDimmer.send();
}
}
private void sendLights() {
ObjectMapper mapper = new ObjectMapper();
String json = "";
try {
json = mapper.writeValueAsString(ils.getLights());
} catch (JsonProcessingException e) {
e.printStackTrace();
}
// output
sendMessage(json);
}
}

If your server is using readLine(), as is probable, it will block until you close the connection, because you aren't sending a line.
Add bw.newLine() before the flush().
EDIT As predicted, your server isn't sending lines, so it needs the same treatment as above. However there is an anterior problem:
while( (in = br.readLine()) != null ){
cmd.add(in);
}
This loop in the server cannot possibly exit until the client closes the connection. You should process a line at a time in the server, or else moderate your expectations of the client's behaviour.

Network communication isn´t working

I made a little game. Now i want to get the highscore from my Server. The code on the client:
private int getOnlineHighscore() {
int highscore = 0;
try {
socket = new Socket("localhost", 444);
input = socket.getInputStream();
System.out.println(input);
highscore = input.read();
input.close();
socket.close();
input = null;
socket = null;
} catch (Exception e) {
System.out.println("Verbindung fehlgeschlagen!");
}
System.out.println(highscore);
return highscore;
}
And on the Server:
import java.io.*;
import java.net.*;
public class ReadServer extends Thread {
private Socket socket;
public ReadServer(Socket socket) {
super();
this.socket = socket;
}
public void run() {
try {
System.out.println(socket.getInetAddress());
String result = "";
try (BufferedReader br = new BufferedReader(
new FileReader(System.getProperty("user.home") + "/AppData/Roaming/GameServer/.sg"))) {
StringBuilder sb = new StringBuilder();
String line = br.readLine();
System.out.println("2");
while (line != null) {
sb.append(line);
sb.append(System.lineSeparator());
line = br.readLine();
}
System.out.println("3");
result = sb.toString();
System.out.println("3.5");
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("4");
socket.getOutputStream().write(Integer.parseInt(result));
System.out.println(result);
} catch (Exception e) {
}
try {
socket.close();
} catch (Exception e) {
}
}
public static void main(String[] Args) {
Socket socket = null;
ServerSocket server = null;
try {
server = new ServerSocket(444);
while (true) {
socket = server.accept();
new ReadServer(socket).start();
}
} catch (Exception e) {
}
try {
server.close();
} catch (Exception e) {
}
}
}
If I run it, the client function returns:
-1
The server writes in the console(not important I think):
/127.0.0.1
2
3
3.5
4
How to solve the problem? I want to send an int stored on my Server to a client.
-Jakob

-1 is returned by read() to specify end of stream , make sure data to be read is being returned .

What is the highscore stored in the file? I believe the file is empty and it fails on parsing the integer but as your catch block is empty, you don't see the exception. Put printStacktrace or rethrow.
Another problem is that OutputStream sends only bytes and therefore write method sends only low 8 bits. To send int wrap the stream with DataOutputStream and DataInputStream on the client side.

Java SocketException: Software caused connection abort

I'm trying to develop a client-server exchange program, and when I try to send data from client to server, I'm running into a SocketException. I've looked at other answers but none of them fit my exact case; I have two calls to osw.write, and only one of them works.
Client:
package me.primesearch.client;
import java.math.BigInteger;
import java.net.*;
import java.io.*;
public class PrimeSearchClient {
public static void main(String[] args) throws IOException{
Socket connection = null;
try{
/** Define a host server */
String host = "localhost";
/** Define a port */
int port = 25564;
StringBuffer instr = new StringBuffer();
System.out.println("SocketClient initialized");
/** Obtain an address object of the server */
InetAddress address = InetAddress.getByName(host);
/** Establish a socket connetion */
connection = new Socket(address, port);
/** Instantiate a BufferedOutputStream object */
BufferedOutputStream bos = new BufferedOutputStream(connection.
getOutputStream());
/** Instantiate a BufferedInputStream object for reading
/** Instantiate a BufferedInputStream object for reading
* incoming socket streams.
*/
BufferedInputStream bis = new BufferedInputStream(connection.
getInputStream());
/**Instantiate an InputStreamReader with the optional
* character encoding.
*/
InputStreamReader isr = new InputStreamReader(bis, "US-ASCII");
/**Read the socket's InputStream and append to a StringBuffer */
int c;
/** Instantiate an OutputStreamWriter object with the optional character
* encoding.
*/
OutputStreamWriter osw = new OutputStreamWriter(bos, "US-ASCII");
while(true){
String process = "drq " + (char) 13;
/** Write across the socket connection and flush the buffer */
osw.write(process);
osw.flush();
while ( (c = isr.read()) != 13)
instr.append( (char) c);
for(int i=0;i<50;i++){
BigInteger offset=new BigInteger(instr.toString()).add(BigInteger.valueOf(i));
if(isProbablyPrime(offset)){
process = "pri" + " " + offset + " " + (offset.divide(new BigInteger("50"))).toString() + (char) 13;
System.out.println(process);
/** Write across the socket connection and flush the buffer */
osw.write(process); //This doesn't work
osw.flush();
System.out.println("Prime found at " + offset);
}
}
}
} catch(IOException e) {
e.printStackTrace();
} finally {
connection.close();
}
}
public static boolean isProbablyPrime(BigInteger n) {
if(n.longValue()!=0){
BigInteger lessOne = n.subtract(BigInteger.ONE);
// get the next prime from one less than number and check with the number
return lessOne.nextProbablePrime().compareTo(n) == 0;
}
return false;
}
}
Server:
package me.primesearch.server;
import java.net.*;
import java.io.*;
public class PrimeSearchServer implements Runnable {
private Socket connection;
#SuppressWarnings("unused")
private int ID;
PrimeSearchServer(Socket s, int i) {
this.connection = s;
this.ID = i;
}
#SuppressWarnings("resource")
public static void main(String[] args) {
int port = 25564;
int count = 0;
try{
ServerSocket socket1 = new ServerSocket(port);
System.out.println("MultipleSocketServer Initialized");
while (true) {
Socket connection = socket1.accept();
Runnable runnable = new PrimeSearchServer(connection, ++count);
Thread thread = new Thread(runnable);
thread.start();
}
}
catch (Exception e) {
e.printStackTrace();
}
}
#Override
public void run() {
try {
BufferedInputStream is = new BufferedInputStream(connection.getInputStream());
InputStreamReader isr = new InputStreamReader(is);
int character;
StringBuffer process = new StringBuffer();
while((character = isr.read()) != 13) {
process.append((char)character);
}
System.out.println(process);
String returnCode="0";
if(process.toString().split(" ")[0].equals("drq")){
System.out.println("Job request recieved");
File file = new File("packages.txt");
//Process input
try (BufferedReader br = new BufferedReader(new FileReader(file))) {
String line;
String prevLine="";
boolean i = false;
int count=0;
while ((line = br.readLine()) != null) {
System.out.println("Looking for a package to send");
// process the line.
if(line.equals("0")){
System.out.println("Sending package " + count);
returnCode = Integer.toString(count);
i = true;
break;
}
prevLine = line;
count++;
System.out.println("No packages found");
}
if(!i){
returnCode = prevLine;
try(PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("packages.txt", true)))) {
System.out.println("Creating new package");
out.println("0");
returnCode=Integer.toString(count);
}catch (IOException e) {
e.printStackTrace();
}
}
}
} else if (process.toString().split(" ")[0].equals("pri")){
System.out.println("Prime request recieved");
try(PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("primes.txt", true)))) {
out.println(Integer.parseInt(process.toString().split(" ")[1]));
}catch (IOException e) {
e.printStackTrace();
}
updateLine(Integer.parseInt(process.toString().split(" ")[2]));
}
BufferedOutputStream os = new BufferedOutputStream(connection.getOutputStream());
OutputStreamWriter osw = new OutputStreamWriter(os, "US-ASCII");
osw.write(returnCode + (char)13);
osw.flush();
process = new StringBuffer();
}
catch (Exception e) {
System.out.println(e);
}
finally {
try {
connection.close();
}
catch (IOException e){
e.printStackTrace();
}
}
}
private void updateLine(int lines) throws IOException {
String data="packages.txt";
BufferedReader file = new BufferedReader(new FileReader(data));
String input = "";
String line;
for(int i=0;i<lines;i++){
input+=file.readLine()+System.lineSeparator();
}
file.readLine();
while ((line = file.readLine()) != null)
input += line + System.lineSeparator();
FileOutputStream os = new FileOutputStream(data);
os.write(input.getBytes());
file.close();
os.close();
}
}
Sorry if the indenting on the code looks a bit strange, I'm not used to using stack overflow.

You are closing the socket in your server class:
finally {
try {
connection.close();
}
catch (IOException e){
e.printStackTrace();
}
}

I think this is the problem. This is the first message you're sending to the server.
Client
String process = "drq " + (char) 13;
osw.write(process);
osw.flush();
And since your server stops reading after it gets a 13 char it closes the connection after it reads the first message.
Server
while((character = isr.read()) != 13) {
process.append((char)character);
}

I was getting the same exception when running functional test using TestNG. For me it was a version issue. Uninstalling it and installing older version fixed my issue. Read the following post for information.
https://github.com/cbeust/testng-eclipse/issues/91

BufferedReader from server does not work

In this code I can correctly receive a request using BufferedReader inClient, created on the client socket.
Then I send the request to the server and I see the server gets it.
But then, when I try to read the reply from the server (using BufferedReader inServer on the socket of the server), it always ends in IOException: Impossible read from server.
I am referring to the block ################
Do you know any possible reasons?
import java.io.*;
import java.net.Socket;
import java.net.ServerSocket;
import java.net.InetAddress;
import java.net.UnknownHostException;
public class ProxyMain {
public static void main(String argv[]) {
int proxyPort = 55554;
String proxyAddr = "127.0.0.1";
ServerSocket proxySocket = null;
try {
proxySocket = new ServerSocket(proxyPort, 50, InetAddress.getByName("127.0.0.1"));
}
catch (Exception e) {
System.err.println("Impossible to create socket server!");
System.out.flush();
System.exit(1);
}
System.out.printf("Proxy active on port: %d and on address %s\n", proxyPort, proxySocket.getInetAddress());
System.out.println();
while (true) {
Socket client = null;
Socket sockServ = null;
BufferedReader inClient = null;
PrintWriter outClient = null;
BufferedReader inServer = null;
PrintWriter outServer = null;
String request = new String();
String tmp = new String();
String reply = new String();
String tmpReply = new String();
try {
client = proxySocket.accept();
System.out.println("Connected to: ");
System.out.println(client.getInetAddress().toString());
System.out.printf("On port %d\n", client.getPort());
System.out.println();
inClient = new BufferedReader(new InputStreamReader(client.getInputStream()));
outClient = new PrintWriter(client.getOutputStream(), true);
}
/*catch (IOException e) {
System.err.println("Couldn't get I/O for connection accepted");
System.exit(1);
}*/
catch (Exception e) {
System.out.println("Error occurred!");
System.exit(1);
}
System.out.println("Received request:");
try{
for (int i = 0; i<2; i++) {
tmp = inClient.readLine();
request = request + tmp;
}
inClient.close();
}
catch (IOException ioe) {
System.err.println("Impossible to read mhttp request!");
System.exit(1);
}
System.out.println(request);
System.out.println();
try {
sockServ = new Socket("127.0.0.1", 55555);
outServer = new PrintWriter(sockServ.getOutputStream(), true);
inServer = new BufferedReader(new InputStreamReader(sockServ.getInputStream()));
}
catch (UnknownHostException e) {
System.err.println("Don't know about host: 127.0.0.1:55555");
System.exit(1);
}
catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to: 127.0.0.1:55555");
System.exit(1);
}
outServer.println(request);
outServer.close();
try {
#################################################
while ((tmpReply = inServer.readLine()) != null) {
System.out.println(tmpReply);
reply = reply + tmpReply;
}
inServer.close();
sockServ.close();
}
catch (IOException ioe) {
System.err.println("Impossible to read from server!");
System.exit(1);
}
outClient.println(reply);
outClient.close();
try {
client.close();
}
catch (IOException ioe) {
System.err.printf("Impossible to close connection with %s:%d\n", client.getInetAddress().toString(), client.getPort());
}
}
}
}
UPDATE:
It seems that if I do:
boolean res = inServer.ready();
it always return false.
So Server is not ready to send the reply but this is strange...with my Project in C e Python it worked immediately. Why should java be different?

When you close outServer, you close the underlying socket. if you just want to close the output and keep the input open, you need to use Socket.shutdownOutput(). note, you have the same problem when you close inClient.

This works, maybe you can get some ideas from it...
ChatServer - broadcasts to all connected clients
In one command prompt: java ChartServer
In another: java ChatClient localhost (or the ip address of where the server is running)
And another: java ChatClient localhost (or the ip address of where the server is running)
Start chatting in the client windows.
Server like this...
// xagyg wrote this, but you can copy it
import java.io.*;
import java.net.*;
import java.util.*;
public class ChatServer {
public static List list = new ArrayList();
public static void main(String[] args) throws Exception {
ServerSocket svr = new ServerSocket(4444);
System.out.println("Chat Server started!");
while (true) {
try {
Socket s = svr.accept();
synchronized(list) {
list.add(s);
}
new Handler(s, list).start();
}
catch (IOException e) {
// print out the error, but continue!
System.err.println(e);
}
}
}
}
class Handler extends Thread {
private Socket s;
private String ipaddress;
private List list;
Handler (Socket s, List list) throws Exception {
this.s = s;
ipaddress = s.getInetAddress().toString();
this.list = list;
}
public void run () {
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(s.getInputStream()));
String message;
//MyDialog x = (MyDialog)map.get(ipaddress.substring(1));
while ((message = reader.readLine()) != null) {
if (message.equals("quit")) {
synchronized(list) {
list.remove(s);
}
break;
}
synchronized(list) {
for (Object object: list) {
Socket socket = (Socket)object;
if (socket==s) continue;
PrintWriter writer = new PrintWriter(socket.getOutputStream());
writer.println(ipaddress + ": " + message);
writer.flush();
}
}
}
try { reader.close(); } catch (Exception e) {}
}
catch (Exception e) {
System.err.println(e);
}
}
}
Client like this ...
// xagyg wrote this, but you can copy it
import java.util.*;
import java.io.*;
import java.net.*;
public class ChatClient {
public static void main(String[] args) throws Exception {
Socket s = new Socket(args[0], 4444);
BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));
PrintWriter out = new PrintWriter(s.getOutputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String message;
new SocketReader(in).start();
while ((message = reader.readLine())!=null) {
out.println(message);
out.flush();
if (message.equals("quit")) break;
}
in.close();
out.close();
}
}
class SocketReader extends Thread {
BufferedReader in;
public SocketReader(BufferedReader in) {
this.in = in;
}
public void run() {
String message;
try {
while ((message = in.readLine())!=null) {
System.out.println(message);
}
}
catch (Exception e) {
throw new RuntimeException(e);
}
}
}