In this article, we will discuss java.net.connectexception: connection refused: connect error while installing apk. We will discuss what this means, why it occurs and how to fix this error in detail. Firstly, let us understand the different parts of this error individually.
What is Java.net.connectionexception?
Java.net.connectionexception is a common exception in Java that is related to networking. The users encounter this exception when making a TCP connection in a server from an application of the client. This exception is handled in a try-catch block. There are three causes of this exception:
- The user tries to connect to a server. If the server is not started, then there is no connection. Hence, the user gets this exception.
- The users use a combination of host and port to connect to a server. If the combination is incorrect, then the users might encounter this exception.
- The third possibility might be that a firewall blocks the connection for some address or some ports in the user’s device.
The users can catch this exception in a program. They have to connect to the server via programs and establish a TCP connection with the server. The host and port combination they are using must be correct. The program that the users must use to connect to the server is java.net.Socket class. If they use an incorrect combination of host and port in their program, the socket will throw an exception. The users have to keep a check on the stack trace to see what is going wrong in their code. If there is no visible stack trace, it will mean that their program code is successfully connected to the server. If it throws an exception then, the users have to check their connection details. They must make their firewall settings correct so that it does not prevent any connection.
The users can also check the connection from the command line interface. They can use the ping command if their server is running or not. The server has to run as it is the one they are trying to connect with. If the server is running, then they will see that information about the packages being sent and received. The users can also use Telnet to connect to a host address. We can pass an exact port in Telnet, or it will use its default port of 23. The server they are trying to reach might run successfully, and the host and port combination can also be correct. Still, the users must keep in mind that the telnet and ping command does not always work. A firewall might block internet traffic which can be another cause for failure.
Have a look: Error Code d0111-How to Fix?
What is java.net.connectexception: connection refused: connect error while installing apk
Java.net.connectionexception:connection refused is a typical Java networking error. When a user is working with client-server architecture, he can get this error while trying to connect to the server from the client. The user will use the TCP connection to connect from the client to the server. In distributed Java applications, this is still a frequent problem. This error also comes in the case of remote method invocation as TCP-IP protocol is used by it too. A user must provide exception handling while writing for client socket code.
Why the client getting this error
When a client tries to connect to a TCP port but is not able to do so then, he gets java.net.connectexception: connection refused: connect error while installing apk. Some of the reasons why the client can get this error are:
Client or server is not in Network:
Java throws Java.net.connectionexception:connection refused error when the client or server or both of them are not connected to any network such as internet or LAN. The client-side will get this error if there is no connection from the client as well as the server.
If a server is not running:
This error is expected when the server is down. If a server is down and is not working, then the users will get this error. They can use the ping command to check the server’s working and listen to the port.
The server is not listening to a port:
Sometimes, a server might run, but it stops listening to the port when the client tries to connect with it. The server might also listen to a different port. The user has to verify his configuration to find out the problems with the server. When a user is working on a big project, the configuration files are in a hierarchy. In such a case, the default configuration might occur, and some settings might override the correct settings of the server.
Firewall does not permit host-port combination:
Firewalls are used to protect private networks. Every corporate network makes use of firewalls. If a company is connecting to another company’s network, then a firewall request needs to be raised from both companies. This is done to ensure that both the companies permit the port number and IP address of each other. When the firewall of one company does not allow this connection, then this error occurs.
Incorrect Host-Port Combination:
If a host-port combination is incorrect then, it might be a reason for this error. This error occurs for two reasons. The first reason is that the user is providing an incorrect host-port combination to the server. Another reason is that on the server-side, the host-port combination gas has been changed. In such cases, the user has to check the configuration on both the client-side as well as the server-side. The user has to fix the configuration issues to avoid connection refused exceptions on the client-side as well as the server-side.
Wrong protocol in the Connection String:
HTTP, RMI, and TCP are high-end protocols. When a user passes a connection string, he must make sure that he is passing the correct protocol as well. The protocol has to be the one, that the server is expecting. For example, if a server has given its services with HTTP, then the connection string must begin with HTTP only.
read also: Error Code 901
How to fix java.net.connectexception: connection refused: connect error while installing apk
Sometimes we get an error in android as- “java.net.connectexception: connection refused: connect error while installing apk” This error occurs when the android is running by the users. The connection gets refused when a user is running a react-native android. The error might appear as some vital information might be missing when we are running the android. Sometimes, a user does not set up the IP address for the local host properly. In such a case, the user has to force Java to use the IP address he adds by adding a new environment variable.
This error also means that the IP porta user is trying to connect has no service listening to it. The user can be trying to connect to the wrong IP port or host port. The user might not start the server, or the backlog queue is packed on the server-side. The server can also be listening to faulty connections. When this error occurs, the user must check the hostname and the port address that he is trying to connect with. He must manage the server-side to listen to the host or port address correctly. He must check the firewall not to block any connections.
There are few things a user can do to fix this error:
Basic solutions steps:
- The user can start to connect the client-side using Putty or Telnet manually. If he can do so, it is clear that the problem lies on the client’s side. He has to fix the issue on the client machine.
- The user can connect his client socket to the remote ServerSocket. The line of code for this is [ ” Socket clientSocket = new” and “Socket(servername, 5000);” ] instead of using [“Socket clientSocket = new” and “Socket(“localhost”, 5000);” ]. The serverName connected by the client should be matching with the name or IP of the box on which the user’s server socket is instantiated. The client machine should be able to reach the name. The IP address is most important in this case. The client machine should be able to reach the IP address. Sometimes, when the user runs the server machine before running a client machine, then it might also fix this error.
- The users can even browse the PC and use the same URL in some cases. The user has to get the IP of his machine. He can use the ipconfig command to do so. The users can also use a specific line of codes to add the IP and the new port manually. This will let the users connect to the server without any problem.
- Sometimes, there are issues with the database server as well. The database server which the user uses to connect may be working fine with open port, accepting all connections but still, the users will get this error. There are issues with the user’s internet as well, as sometimes the user’s internet connection does not allow to connect to a server. In such cases, the users can change their connection details. The issue will be solved, and the users will stop getting this error.
- Changing the socket name of the server can also solve this issue sometimes. If the user changes the address from IPv4 to IPv6, this error stops coming. Again, putting a checkmark near settings might also solve the issue. The user has to click on the right side of the taskbar. Then he has to right-click on the docker and tap on the settings.
- If a user closes serversocket inside a for loop, then he can get this error. The loop tries to accept the clients inside it and ends up generating the error. The user has to make sure, he uses socket.close() to fix this error.
- Changing the DNS might also help with the issue. This can also fix the error.
- The users have to make sure that they initialize the server so that the client does not connect to the wrong IP or port.
- Sometimes, there are permission errors in the files. The permission that we give in a file is not correct. These permissions have to fix to solve the error java.net.connectexception: connection refused: connect error while installing apk.
In this article, we tried to learn about the “java.net.connectexception: connection refused: connect error while installing apk” error. We tried to learn the terms separately and then understood this error. We learned about Java.net.connectionexception, and Java.net.connectionexception:connection refused. Already reasons mentioned for the Java.net.connectionexception:connection refused error in the article. Then we learned about Java.net.connectionexception:connection refused: connect error while installing apk error. This error occurs when the connection gets denied when a user runs a react-native android, and the android is running by the user. There are few methods to fix this error.