Как исправить ошибку java net socketexception

You should inspect full trace very carefully,

I’ve a server socket application and fixed a java.net.SocketException: Connection reset case.

In my case it happens while reading from a clientSocket Socket object which is closed its connection because of some reason. (Network lost,firewall or application crash or intended close)

Actually I was re-establishing connection when I got an error while reading from this Socket object.

Socket clientSocket = ServerSocket.accept();
is = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
int readed = is.read(); // WHERE ERROR STARTS !!!

The interesting thing is for my JAVA Socket if a client connects to my ServerSocket and close its connection without sending anything is.read() is being called repeatedly.It seems because of being in an infinite while loop for reading from this socket you try to read from a closed connection.
If you use something like below for read operation;

while(true)
{
  Receive();
}

Then you get a stackTrace something like below on and on

java.net.SocketException: Socket is closed
    at java.net.ServerSocket.accept(ServerSocket.java:494)

What I did is just closing ServerSocket and renewing my connection and waiting for further incoming client connections

String Receive() throws Exception
{
try {                   
            int readed = is.read();
           ....
}catch(Exception e)
{
        tryReConnect();
        logit(); //etc
}


//...
}

This reestablises my connection for unknown client socket losts

private void tryReConnect()
        {
            try
            {
                ServerSocket.close();
                //empty my old lost connection and let it get by garbage col. immediately 
                clientSocket=null;
                System.gc();
                //Wait a new client Socket connection and address this to my local variable
                clientSocket= ServerSocket.accept(); // Waiting for another Connection
                System.out.println("Connection established...");
            }catch (Exception e) {
                String message="ReConnect not successful "+e.getMessage();
                logit();//etc...
            }
        }

I couldn’t find another way because as you see from below image you can’t understand whether connection is lost or not without a try and catch ,because everything seems right . I got this snapshot while I was getting Connection reset continuously.

A SocketException Connection reset is one of the most common Runtime errors you can find in Java applications. As the name implies, it happens during a network connection which terminates abruptly. In this tutorial we will teach you which is the best action plan to find the root cause of the issue.

What is a “Connection reset” and which are the possible causes?

“Connection reset” simply means that you received a TCP RST. This occurs when your peer receives data that it can’t process, and there can be various reasons for this. The simplest one is when you close the socket and then write more data on the output stream. Then, when you send more data on that stream anyway, the peer rejects it with an RST to let you know it isn’t listening.

A slightly different case is “java.net.SocketException: Connection reset by peer”. This error hints that the remote host sent the connection reset (i.e., the host that the Java application is connecting to).

There are several possible causes for this error, such as:

Firewall

Firstly, if the firewall has a rule that blocks all incoming traffic from the client, it may send an RST packet to the server to reset the connection as soon as it receives a SYN packet from the client.

Also, if the firewall has a rule that allows incoming traffic from the client, but blocks all outgoing traffic from the server to the client, it may send an RST packet to the client to reset the connection when it receives a SYN-ACK packet from the server.

Then, if the firewall has a rule that allows incoming traffic from the client, but blocks all outgoing traffic from the server to the client based on the port number or protocol, it may send an RST packet to the client to reset the connection when it receives a SYN-ACK packet from the server.

Finally, if the firewall has a rule that allows incoming traffic from the client, but blocks all outgoing traffic from the server to the client based on the content of the packets, it may send an RST packet to the client to reset the connection when it receives a SYN-ACK packet from the server that contains data that matches the specified criteria.

Network Scanner

A network scanner can cause a TCP connection RESET between a client and a server by sending a forged RST packet to one or both of the devices.

For example, a network scanner could send a forged RST packet to the client, pretending to be the server. The client would receive the RST packet and believe that the server wants to reset the connection. So it would send an RST packet back to the server and close the connection.

Alternatively, the network scanner could send a forged RST packet to the server, pretending to be the client. The server would receive the RST packet and believe that the client wants to reset the connection, so it would send an RST packet back to the client and close the connection.

In either case, the network scanner could use this technique to disrupt the communication between the client and the server.

Network switch

A network switch can cause a TCP connection RESET between a client and a server when the connection is idle if the switch has a feature called “TCP idle timeout” enabled. This feature allows the switch to close idle TCP connections after a certain period of inactivity. This will result in a premature termination of the connection between the client and the server at the network layer.

Databases

In some cases, the database server may be terminating the connection. This can be due, for example, to a configuration (e.g. timeout period) of the Database server. It can also be related to a defect in the Database driver.

You can manage most of database timeouts/stale connection issues with a proper configuration of Datasource validation. Learn more here: How to validate Database connections in JBoss / WildFly

Client application

Finally, there can be an issue with the Java Client application connecting to the server. A common case is a bug in the software. But it can be as well a misconfiguration or something in the Client OS settings

Finding the root cause

After discussing all possible causes of a “java.net.SocketException: Connection reset”, let’s see how to find the root cause. If your server logs/system log do not provide any extra clue, the best option is to start a dump session.

Here are some things to look for in a dump session:

• If the client is initiating the disconnect, it will typically send a FIN packet to the server to close the connection. You can use tcpdump or a similar tool to capture and inspect the packets being sent over the network.
• If the server is initiating the disconnect, it will typically send a RST packet in response to a client request, or close the connection after a period of inactivity. You can use tcpdump or a similar tool to capture and inspect the packets being sent over the network.

For example, Linux users can start the tcpdump command:

 tcpdump -i eth0  port 8080  and '(tcp-syn|tcp-rst)!=0' 

The above tcpdump command will list SYN (connection attempts) and RST (reset connections) on port 8080. Let’s see a practical example:

$ netstat -na

Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 127.0.0.1:8080          0.0.0.0:*               LISTEN

$ tcpdump -i eth0  port 8080  and '(tcp-syn|tcp-rst)!=0' 

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
20:34:50.569441 IP localhost.8080 > localhost.41300: Flags [S], seq 1779073596, win 65535, options [mss 65495,sackOK,TS val 838312 ecr 0,nop,wscale 7], length 0
20:34:50.569474 IP localhost.41300 > localhost.8080: Flags [R], seq 0, win 0, length 0

This dump shows that the client is sending a SYN packet to initiate the connection. Then, the server is sending a RST packet to reset the connection. For example, it could be a firewall blocking the connection. You can use tools such as iptables or ufw to view and configure the firewall rules on the system.

Conclusion

This article was a walk through the analysis of the Connection reset error in a Java applicaion. In most cases, to further understand the cause of the error, you can try examining other packets being exchanged between the client and server, and analyzing the system activity.

The “Internal Exception: java.net.SocketException: Connection reset” error can seem like a simple internet connectivity issue at first glance, but it’s much more than that. This error has been around for years and doesn’t have a single fixed cause.

Accordingly, users have managed to resolve it with various unlikely methods, like creating a new installation profile or adjusting the graphic settings. Others have placed the blame on server-side issues, although the devs continue to deny this.

Leaving that controversy aside, the important detail is that even though there’s no official patch from the devs, there are time-tested solutions that have helped numerous users. We’ve compiled a list of such fixes in this article.

Before anything, restart your PC and router. Once that’s done, run Minecraft as an administrator. If the error persists, move on to the solutions to start troubleshooting.

VPN-related Fixes

We’ve found this error to be primarily related to VPNs, both in good and bad ways. Some users reported that this error didn’t occur when connected to a VPN. Others found that a VPN didn’t help at first, but after trying a few different clients and server locations, the error no longer occurred.

On the other hand, some users first encountered this error when playing with a VPN. In such cases, it would be best to disable the VPN instead. 

Specifically, after limited testing, the Minecraft Community Support Discord members found Hamachi VPN to be one of the main causes of this error. If you’re using Hamachi VPN as well, we recommend uninstalling Hamachi, or atleast disabling it, and checking if the error is resolved.

Check Network Configurations

The reason VPNs have resolved this issue for so many users has to do with your IP address on the current network. As such, simply connecting to a different network could be all that’s needed to fix this error.

Configuring a couple of global TCP settings has also been one of the most successful fixes for this error. Here’s how you can apply this fix:

1. Press Win + R, type cmd, and press CTRL + Shift + Enter.
2. Type netsh interface tcp show global and press Enter.
   
3. Check the value of Receive-Side Scaling State. If it’s disabled, type netsh interface tcp set global rss=enabled and press enter.
4. Next, check the value of Receive Window Auto-Tuning Level. If it’s disabled, type netsh interface tcp set global autotuninglevel=normal and press enter.
   
5. Exit command prompt, launch Minecraft, and check if the error is resolved.

If the error persists, we recommend manually changing the DNS server as the next step. If that doesn’t help either, execute the commands listed below in command prompt. They’ll perform a bunch of useful actions, including clearing your DNS cache and renewing your IP.

Java-related Fixes

The official Minecraft launcher handles Java installation for Minecraft automatically, so generally, it’s not something the player needs to worry about. But when running dedicated servers on older Java versions, it is essential.

First, you’ll want to download and install the JDK. Some users have had success with the latest version, while others had to install older versions like JDK16 to resolve the error. So essentially, it’s worth trying out different versions.

Next, you’ll also want to ensure JDK is allowed through the firewall. If you’re using any third-party firewall, we recommend temporarily disabling it to check if the error gets fixed. In the case of Windows Firewall, here are the steps you should follow:

1. Press Win + R, type control firewall.cpl, and press Enter.
2. Click on Allow an app or feature through Windows Defender Firewall.
   
3. Click on Change settings and accept any prompts.
   
4. Scroll down and select OpenJDK Platform Binary. Ensure the checkboxes in both the Private and Public fields are enabled.
5. If you don’t find this entry, click on Allow another app > Browse.
   
6. Select javaw.exe and select Open > Add from the following location:
   C:Program Files (x86)Minecraftruntimejava-runtime-alphawindows-x64java-runtime-alphabin
7. Finally, press OK, launch Minecraft, and check if you still get the error.

Migrate to Microsoft Account

Some users found that the error stopped occurring after they migrated their Mojang accounts to Microsoft. The Minecraft Help Center has extensive guides that answer most of the common queries regarding the migration process, so we highly recommend referring to said guides if you need help with the migration.

Workaround with Epic Games Launcher

If you start downloading any random game in the Epic Games Launcher and then try to launch Minecraft, chances are, you won’t encounter the error. There’s no sound reasoning for why this workaround works, but the important part is that it did let countless users play without the error, so it’s worth trying.

Create New Launcher Profile

This is another solution recommended by Mojang, with a proven record. Here’s how you can use a new installation profile:

1. Run the Minecraft launcher and click on Installations.
   
2. Click on New Installation and name it as you please.
3. Set the version to an older one (e.g., 1.18.2 ) and try launching Minecraft.

Check Visual Settings

Downgrading the game graphics has resolved this error for numerous players. Even teleporting to an unmodified area has been helpful in some cases. This is possibly because the server is unable to handle how fast you’re loading the world at your current settings. Here’s what we recommend:

1. In Minecraft, enter a different world if necessary and go to Options > Video Settings.
   
2. First, turn off Full screen and try lowering the resolution.
   
3. Restart Minecraft and check if the error is resolved.
4. Reduce the Render Distance to 12 chunks or lower, then restart and check again. Additionally, toning down the Graphics and Simulation distance settings can help with lag.
   
5. Finally, one user also found that uninstalling all the texture packs fixed the problem. So, if the error still persists, this may be worth trying.

Server-related Fixes

There are a number of server-related solutions useful for resolving this error. We recommend trying them in the following order:

• First, increase the server memory. The default amount (1GB) is known to cause connection issues and crashes as the limit is easily reached.
• Try switching to a lower server version.
• If you’re the host, you could try copying the private server files to another location. If you encounter problems moving any files, said files could be the cause of the error.
• Additionally, starting a new world with a new server host could also help.

Reinstall Minecraft

If the error still persists, uninstalling and reinstalling Minecraft is likely the final option at this point. You’ll want to copy the saves from the .minecraft folder in %appdata% before uninstalling, though. Additionally, a PC reset is overkill for this error, but if you’ve backed up your files elsewhere and playing Minecraft means a lot to you, then this is an option to consider as well.