How to fix java.net.SocketException: Broken pipe, Connection reset, and Too many open files in Java?

In this blog, I plan to talk about some common exceptions and errors that arise while using sockets. Quite often, these socket issues arise out of application bugs, system settings, or system load. It might be an unnecessary delay to go to product teams, only to discover that the issue can be resolved by tuning/configuring your local settings. Understanding these messages will not only help resolve the issues but also make a conscious effort in avoiding these scenarios while developing applications.

I have tried to make the blog as much platform-independent as possible :). You may want to search the web if you wish to know the specifics. Though, if you are not familiar with Socket programming in Java then I also suggest you check the Java: Socket Programming Simplified, a free course on Udemy.

How to fix  java.net.SocketException: Broken pipe, Connection reset,  and Too many open files in Java?

Now, here are some common Socket related errors in Java, their explanation, and thoughts on how to solve them. 

1. java.net.SocketException: No buffer space available (maximum connections reached?)

This exception is usually observed When connections are being made at a rapid rate. This exception can arise due to one of the following conditions

a. When the number of available ephemeral network ports available for the application are nil.
b. When the system does not have enough main memory to support new connections. (Whenever a socket is created, a part of the memory is allocated for its READ/SEND buffers.. from non-paged kernel memory.)

Solution: In Windows, the number of ephemeral network ports can be increased as directed here to resolve the problem arising out of case 'a'.

The only available solution for case 'b' is to make sure that the network connections are closed properly by the applications. And make sure the rate at which the connections are created does not throttle the kernel memory.

Currently, there are no formally documented approaches available to increase non-paged kernel memory. You can also see these free Java Programming courses to learn more about Socket programming in Java.

2. java.net.SocketException: Broken pipe (UNIX)

A broken pipe error is seen when the remote end of the connection is closed gracefully.
Solution: This exception usually arises when the socket operations performed on either end are not synced.

 

3. java.net.SocketException: Connection reset [Solution]

This exception appears when the remote connection is unexpectedly and forcefully closed due to various reasons like application crashes, system reboot, the hard close of the remote host. Kernel from the remote system sends out packets with the RST bit to the local system.

The local socket on performing any SEND (could be a Keep-alive packet) or RECEIVE operations subsequently fail with this error. Certain combinations of linger settings can also result in packets with an RST bit set.

 

4. java.net.SocketException: Too many open files Solution

An attempt was made to open more than the maximum number of file descriptors allowed in this process. These file descriptors include various other entities along with sockets. This is implementation-dependent and could be either globally, per process, or per thread. On Linux, this is designated by the number {OPEN_MAX}.

Solution: Monitor the application and keep a watch on this. These values may be configurable on certain implementations. On Linux, ulimit can be used.


     

5. java.net.BindException: Address already in use: JVM_Bind/java.net.BindException: Address already in use: NET_Bind

In the case, where the exception arises while doing a socket bind. The reason is that the application is trying to bind a socket to a port/IP/protocol combination that is already in use.

Solution: Avoid this. netstat log will be of help in this case to confirm. If you want to learn more about Socket Programming in Java, I suggest you check the Java: Socket Programming Simplified, a free course on Udemy.

 

6. java.net.BindException: Address already in use: connect

In the case, where the exception arises while doing a socket connection. There are several explanations for this some of the complex, depending on the implementation. Nonetheless, the problem can best be summarized that no local port numbers are available to the client.

This could be because there are a lot of active connections in the local system(also involves sockets in a reuse connections phenomenon).

Or a lot of ports are in TIME_WAIT state(the period between closing a connection and releasing the resources).

Solution: Increase the number of available ports. But if the problem is that there are not many concurrent active connections but in the TIME_WAIT state, then reducing the TIME_WAIT value is a solution. This is platform-dependent. Please consult the OS documents for more information.

 

7. Hang in Socket Write call

This happens when the sockets write buffers do not contain enough free space to accommodate the send data. This usually means the other side of the connection is not reading the data.


That's all about the most common Socket errors and exceptions in Java applications. In this article, we have covered 7 most common Socket related errors and exceptions like Broken Pipe, Connection Reset, Too many open files, address already in use for bind and connect, and no buffer space available in Java and how to deal with them.

If you have worked in Java backend application and written client and server application in Java then you would have definitely seen one of these Socket connection error already. Knowing what causes them and how to fix them can definitely make you a better and more competent Java developer. 



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Thanks for reading this article so far. If you like this article then please share with your friends and colleagues. If you want to learn more about Socket Programming in Java, I suggest you check these advanced core Java courses which contain some references for socket and network programming in Java.