java net ConnectException Connection refused

Question

I m trying to implement a TCP connection  everything works fine from the server s side but when I run the client program  from client computer  I get the following error   java net ConnectException  Connection refused         at java net PlainSocketImpl socketConnect Native Method          at java net PlainSocketImpl doConnect PlainSocketImpl java 351          at java net PlainSocketImpl connectToAddress PlainSocketImpl java 213          at java net PlainSocketImpl connect PlainSocketImpl java 200          at java net SocksSocketImpl connect SocksSocketImpl java 432          at java net Socket connect Socket java 529          at java net Socket connect Socket java 478          at java net Socket  lt init gt  Socket java 375          at java net Socket  lt init gt  Socket java 189          at TCPClient main TCPClient java 13    I tried changing the socket number in case it was in use but to no avail  does anyone know what is causing this error  amp  how to fix it   The Server Code     TCPServer java  import java io    import java net     class TCPServer       public static void main String argv    throws Exception           String fromclient          String toclient           ServerSocket Server   new ServerSocket 5000            System out println  TCPServer Waiting for client on port 5000             while  true                Socket connected   Server accept                System out println   THE CLIENT          connected getInetAddress                               connected getPort       IS CONNECTED                  BufferedReader inFromUser   new BufferedReader                      new InputStreamReader System in                 BufferedReader inFromClient   new BufferedReader                      new InputStreamReader connected getInputStream                   PrintWriter outToClient   new PrintWriter                      connected getOutputStream    true                while  true                     System out println  SEND Type Q or q to Quit                      toclient   inFromUser readLine                     if  toclient equals  q      toclient equals  Q                          outToClient println toclient                       connected close                        break                    else                       outToClient println toclient                                      fromclient   inFromClient readLine                     if  fromclient equals  q      fromclient equals  Q                          connected close                        break                    else                       System out println  RECIEVED     fromclient                                                         The Client Code     TCPClient java  import java io    import java net     class TCPClient       public static void main String argv    throws Exception           String FromServer          String ToServer           Socket clientSocket   new Socket  localhost   5000            BufferedReader inFromUser   new BufferedReader new InputStreamReader                  System in             PrintWriter outToServer   new PrintWriter                  clientSocket getOutputStream    true            BufferedReader inFromServer   new BufferedReader new InputStreamReader                  clientSocket getInputStream               while  true                 FromServer   inFromServer readLine                 if  FromServer equals  q      FromServer equals  Q                      clientSocket close                    break                else                   System out println  RECIEVED     FromServer                   System out println  SEND Type Q or q to Quit                       ToServer   inFromUser readLine                     if  ToServer equals  Q      ToServer equals  q                          outToServer println ToServer                       clientSocket close                        break                    else                       outToServer println ToServer

User · Answer

One point that I would like to add to the answers above is my experience-

"I hosted on my server on localhost and was trying to connect to it through an android emulator by specifying proper URL like http://localhost/my_api/login.php . And I was getting connection refused error"

Point to note - When I just went to browser on the PC and use the same URL (http://localhost/my_api/login.php) I was getting correct response

so the Problem in my case was the term localhost which I replaced with the IP for my server (as your server is hosted on your machine) which made it reachable from my emulator on the same PC.

To get IP for your local machine, you can use ipconfig command on cmd you will get IPv4 something like 192.68.xx.yy Voila ..that's your machine's IP where you have your server hosted. use it then instead of localhost

http://192.168.72.66/my_api/login.php

Note - you won't be able to reach this private IP from any node outside this computer. (In case you need ,you can use Ngnix for that)

User · Answer

i got this error because I closed ServerSocket inside a for loop that try to accept number of clients inside it  I did not finished accepting all clints   so be careful where to close your Socket

User · Answer

I had the same problem  but running the Server before running the Client fixed it

User · Answer

In my case  I had to put a check mark near Expose daemon on tcp   localhost 2375 without TLS in docker setting  on the right side of the task bar  right click on docker  select setting

User · Answer

I had same problem and the problem was that I was not closing socket object After using socket close    problem solved  This code works for me   ClientDemo java  public class ClientDemo       public static void main String   args  throws UnknownHostException              IOException           Socket socket   new Socket  127 0 0 1   55286           OutputStreamWriter os   new OutputStreamWriter socket getOutputStream             os write  Santosh Karna            os flush            socket close              and  ServerDemo java  public class ServerDemo       public static void main String   args  throws IOException           System out println  server is started            ServerSocket serverSocket  new ServerSocket 55286           System out println  server is waiting            Socket socket serverSocket accept            System out println  Client connected            BufferedReader reader new BufferedReader new InputStreamReader socket getInputStream              String str reader readLine            System out println  Client data    str           socket close            serverSocket close

User · Answer

This exception means that there is no service listening on the IP port you are trying to connect to    You are trying to connect to the wrong IP Host or port  You have not started your server  Your server is not listening for connections  On Windows servers  the listen backlog queue is full

User · Answer

You have to connect your client socket to the remote ServerSocket  Instead of  Socket clientSocket   new Socket  localhost   5000    do   Socket clientSocket   new Socket serverName  5000    The client must connect to serverName which should match the name or IP of the box on which your ServerSocket was instantiated  the name must be reachable from the client machine   BTW  It s not the name that is important  it s all about IP addresses

User · Answer

Hope my experience may be useful to someone  I faced the problem with the same exception stack trace and I couldn t understand what the issue was  The Database server which I was trying to connect was running and the port was open and was accepting connections   The issue was with internet connection  The internet connection that I was using was not allowed to connect to the corresponding server  When I changed the connection details  the issue got resolved

User · Answer

I had the same issue  and it turned out to be due to permission of the catalina out file not being correct   It was not writable by the tomcat user   Once I fixed the permissions  the issue got resolved   I got to know that it is a permissions issue from the logs in the tomcat8-initd log file    usr sbin tomcat8  line 40   usr share tomcat8 logs catalina out  Permission denied

User · Answer

I had the same problem with Mqtt broker called vernemq but solved it by adding the following      sudo vmq-admin listener show   to show the list o allowed ips and ports for vernemq     sudo vmq-admin listener start port 1885 -a 0 0 0 0 --mountpoint  appname --nr of acceptors 10 --max connections 20000   to add any ip and your new port  now u should be able to connect without any problem    Hope it solves your problem

User · Answer

I would check    Host name and port you re trying to connect to The server side has managed to start listening correctly There s no firewall blocking the connection   The simplest starting point is probably to try to connect manually from the client machine using telnet or Putty  If that succeeds  then the problem is in your client code  If it doesn t  you need to work out why it hasn t  Wireshark may help you on this front

User · Answer

I changed my DNS network and it fixed the problem

User · Answer

In my case  I gave the socket the name of the server  in my case  raspberrypi    and instead an IPv4 address made it  or to specify  IPv6 was broken  the name resolved to an IPv6

User · Answer

You probably didn t initialize the server or client is trying to connect to wrong ip port

User · Answer

It could be that there is a previous instance of the client still running and listening on port 5000

[java] java.net.ConnectException: Connection refused

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