I'm making a python server running on my computer and java socket client running on my phone. the minute the java tries to connect, the app freezes. Not saying anything in the logcat. I have no idea why...
python 3.5.1:
PORT = 8888
import socket
sock = socket.socket()
sock.bind(("0.0.0.0", PORT))
sock.listen(1)
client = None
while not client:
try:
client = sock.accept()
except:
pass
print(client[1])
java:
static String get_leaderboard() {
Socket sock;
OutputStream out;
InputStream in;
try {
System.out.println("now trying to connect");
sock = new Socket("192.168.1.29", 8888);
System.out.println("connected successfuly");
out = sock.getOutputStream();
in = sock.getInputStream();
return Integer.toString(in.read());
} catch (IOException e) {
e.printStackTrace();
}
return "Error in connection";
but actually, logcat never prints "connected successfuly". just "trying to connect".
This line is wrong:
client = sock.connect()
Servers don't call connect(). Servers call listen() and accept(). Only clients call connect().
Since your server calls bind() and listen(), but not accept(), any client will hang trying to connect to it.
Resources:
https://wiki.python.org/moin/TcpCommunication
https://docs.python.org/3/howto/sockets.html
http://beej.us/guide/bgnet/
Related
I work on a java application.
I got a java socket server mapped with a #ServerEndpoint("/wsock")
Form my javascript code I access the WebSocket from this URL :
ws://192.9.200.73:8084/socketserver/wsock
I want now access to this socket from my java code. But how can I specify the address "socketserver/wsock" ? I've tried something but I got every time an error message.
This is my test :
Socket s = new Socket("localhost/socketserver/wsock", 8084);
But it doesn't work, I got everytime an error message: ".UnknownHostException: localhost/socketserver/wsock"
Any idea?
Thank's
public static boolean pingHost(String host, int port, int timeout) {
try (Socket socket = new Socket()) {
socket.connect(new InetSocketAddress(host, port), timeout);
return true;
} catch (IOException e) {
return false; // Either timeout or unreachable or failed DNS lookup.
}
}
Try this. Its something like ping. If you get true its connected. But your server should be ready.
You use a Websocket client. You can't use a Socket directly for this. There is a superimposed protocol.
I have a working Java client/server program which is very straightforward and basic. This works fine. However, I am now trying to write an Android client, and I have been unable to connect to the server from my android client. I am using almost identical code for the android networking code as I use for the normal client. My android code is simple, all it does is starts this thread from onCreate:
private int serverPort = 8889;
private String serverIP = "192.168.5.230";
private Socket socket = null;
private Thread clientThread = new Thread("ClientThread") {
#Override
public void run() {
try {
socket = new Socket();
socket.connect(new InetSocketAddress(serverIP, serverPort), 1000);
DataInputStream din = new DataInputStream( socket.getInputStream());
DataOutputStream dout = new DataOutputStream(socket.getOutputStream());
while (true) {
String message = din.readUTF();
setPicture("picture1");
}
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
The port is the correct port my server is running on, as is the ip address (which I got from ifconfig since I know you cannot use localhost). When I run my normal pc client with the same port and IP address, the connection goes through. But when I run this code on my android device, the socket timesout when I try to connect.
Does anyone have any suggestions for where I am going wrong?
Double check that you added the permission requirement in the manifest file:
<uses-permission android:name="android.permission.INTERNET" />
But, possibly more importantly, 192.168.x.x is a local or non-routable network so you need to be on the same network, or one that knows how to reach the 192.168.5.230 address. You say that it doesn't work when you try it on your device -- are you running on local wifi when you run or are you on your mobile network? If you're on mobile, try it from wifi.
I have a ServerSocket instance which is listening for connections. When a client connects to it, I would like to get the IP of the connected socket, but can't seem to find the right method to do so.
public void start() {
listenSocket = new ServerSocket(port);
connectionSocket = listenSocket.accept();
}
I've tried calling the following with no luck:
connectionSocket.getLocalAddress();
connectionSocket.getInetAddress.getHostAddress();
listenSocket.getLocalSocketAddress();
None of the above return the correct IP. They either return "/0:0:0:0:0:0:0:1%0" or "0.0.0.0".
What am I doing wrong?
connectionSocket.getRemoteSocketAddress();
What can cause this to happen?
I moved my laptop to a friends house to work on this project. I opened the same port on his xfinity router, and changed all areas of my code to his IP. However it appears that the client is sending a message and the server has never getting past this part of code
System.out.println("running server!");
int nreq = 1;
try{
//SET ME PORT
ServerSocket sock = new ServerSocket(7332);
for(;;){
Socket newsock = sock.accept();
System.out.println("Creating thread...");
//Broken Old Login crap, needs reworked for map n stuff anyhow now
// Thread t = new ThreadHandler(newsock, nreq);
Thread t = new RequestInterpreter(newsock, nreq);
//t.run();
t.start();
nreq++;
}
}
catch(Exception e)
{
e.printStackTrace();
}
It never gets to print "Creating thread". I'm not sure where to begin with what could be going wrong here?
The only thing that has changed is the house, IP, router, and internet. Works everywhere else. What about those changing could block the client from sending a
Here is a test client I wrote also.
import java.io.DataInputStream;
import java.io.PrintWriter;
import java.net.Socket;
public class testClientConnection {
public static void main(String[] args) {
System.out.println("Starting testConnection");
try{
Socket s = new Socket("xx.xx.xx.xxx", 7332);
DataInputStream fromServer = new DataInputStream(s.getInputStream());
PrintWriter toServer = new PrintWriter(s.getOutputStream(), true);
toServer.println("account name");
toServer.println("password");
toServer.println("Login");
System.out.println("Sent message...");
String response = fromServer.readLine().toString();
//Toast the result here? //testing
System.out.println("response: " + response);
if (response.equals("Login Success")) {
System.out.println("Login Success!!!");
}
}
catch(Exception e){ /
}
}
}
HUGE UPDATE!
Ok so my client was an android phone and I turned the wifi off, so it fell onto 4g-LTE. Then it worked. So... Something is blocking the client side code. What might that be?
The firewall on your friend's router is the usual suspect.
Second suspect is the firewall on the target machine.
Try disabling those.
The problem will be NAT on the router.
Servers don't work behind NAT devices unless you set up port-forwarding so that the router knows where to send an incoming request from outside.
I have been trying to get a simple networking test program to run with no results.
Server:
import java.io.*;
import java.net.*;
public class ServerTest {
public static void main(String[] args) {
final int PORT_NUMBER = 44827;
while(true) {
try {
//Listen on port
ServerSocket serverSock = new ServerSocket(PORT_NUMBER);
System.out.println("Listening...");
//Get connection
Socket clientSock = serverSock.accept();
System.out.println("Connected client");
//Get input
BufferedReader br = new BufferedReader(new InputStreamReader(clientSock.getInputStream()));
System.out.println(br.readLine());
br.close();
serverSock.close();
clientSock.close();
} catch(Exception e) {
e.printStackTrace();
}
}
}
}
Client:
import java.io.*;
import java.net.*;
public class ClientTest {
public static void main(String[] args) throws IOException {
final int PORT_NUMBER = 44827;
final String HOSTNAME = "xx.xx.xx.xx";
//Attempt to connect
try {
Socket sock = new Socket(HOSTNAME, PORT_NUMBER);
PrintWriter out = new PrintWriter(sock.getOutputStream(), true);
//Output
out.println("Test");
out.flush();
out.close();
sock.close();
} catch(Exception e) {
e.printStackTrace();
}
}
}
The program works just fine when I use 127.0.0.1 or my internal IP for the hostname. But whenever I switch to my external IP address, it throws a java.net.ConnectException: Connection refused: connect error.
I purposely picked such an uncommon port to see if that was the problem, with no luck.
I can connect with no problems using telnet, but when I try to access the port with canyouseeme.org, it tells me the connection timed out.
I even tried to disable all firewalls and antivirus including the Windows default ones and the router firewall, with all ports forwarded and DMZ enabled, and it still says that the connection timed out. I use Comcast as my ISP, and I doubt that they block such a random port.
When I use a packet tracer, it shows TCP traffic with my computer sending SYN and receiving RST/ACK, so it looks like a standard blocked port, and no other suspicious packet traffic was going on.
I have no idea what is going on at this point; I have pretty much tried every trick I know. If anyone know why the port might be blocked, or at least some way to make the program work, it would be very helpful.
These problem comes under the following situations:
Client and Server, either or both of them are not in network.
Server is not running.
Server is running but not listening on port, client is trying to connect.
Firewall is not permitted for host-port combination.
Host Port combination is incorrect.
Incorrect protocol in Connecting String.
How to solve the problem:
First you ping destination server. If that is pinging properly,
then the client and server are both in network.
Try connected to server host and port using telnet. If you are
able to connect with it, then you're making some mistakes in the client code.
For what it's worth, your code works fine on my system.
I hate to say it, but it sounds like a firewall issue (which I know you've already triple-checked) or a Comcast issue, which is more possible than you might think. I'd test your ISP.
Likely the server socket is only being bound to the localhost address. You can bind it to a specific IP address using the 3-argument form of the constructor.
I assume you are using a Router to connect to Internet. You should do Port Forwarding to let public access your internal network. Have a look at How do you get Java sockets working with public IPs?
I have also written a blog post about Port forwarding, you might wanna have a look :) http://happycoders.wordpress.com/2010/10/03/how-to-setup-a-web-server-by-yourself/
But I still couldn't get this accessed over public IP, working on it now...
I had the same problem because sometimes the client started before server and, when he tried to set up the connection, it couldn't find a running server.
My first (not so elegant) solution was to stop the client for a while using the sleep method:
try {
Thread.sleep(1000);
}
catch (InterruptedException e) {
e.printStackTrace();
}
I use this code just before the client connection, in your example, just before Socket sock = new Socket(HOSTNAME, PORT_NUMBER);
My second solution was based on this answer. Basically I created a method in the client class, this method tries to connect to the server and, if the connection fails, it waits two seconds before retry.
This is my method:
private Socket createClientSocket(String clientName, int port){
boolean scanning = true;
Socket socket = null;
int numberOfTry = 0;
while (scanning && numberOfTry < 10){
numberOfTry++;
try {
socket = new Socket(clientName, port);
scanning = false;
} catch (IOException e) {
try {
Thread.sleep(2000);
} catch (InterruptedException ie) {
ie.printStackTrace();
}
}
}
return socket;
}
As you can see this method tries to create a socket for ten times, then returns a null value for socket, so be carefull and check the result.
Your code should become:
Socket sock = createClientSocket(HOSTNAME, PORT_NUMBER);
if(null == sock){ //log error... }
This solution helped me, I hope it helps you as well. ;-)