How to Increase TCP/IP Connections in Linux

Guide to adjust the number of TCP/IP connections for Linux servers

Linux systems are often used in servers and network applications. Administrators often encounter the problem that the number of TCP/IP connections reaches the upper limit, resulting in user connection errors. This article will guide you how to improve the maximum number of TCP/IP connections in Linux systems.

Understanding TCP/IP connection number

TCP/IP (Transmission Control Protocol/Internet Protocol) is the basic communication protocol of the Internet. Each TCP connection requires system resources. When there are too many active connections, the system may reject new connections or slow down.

By increasing the maximum number of connections allowed, server performance can be improved and more concurrent users can be handled.

Check the current number of Linux connections limits

Before changing settings, it is best to use the following sysctl command to understand the maximum number of TCP connections allowed by the system:

 sysctl net.ipv4.tcp_max_syn_backlog

This command displays the number of incomplete connections allowed. Additionally, to see the total number of available file descriptors (which affects the maximum number of connections), use:

 ulimit -n 

The output of this command indicates the limits for the currently open file, including the TCP connection.

Increase TCP connection limits in Linux

To increase the maximum number of TCP/IP connections, several settings in the system configuration file need to be changed.

1. Increase the number of TCP connections in Linux

The tcp_max_syn_backlog parameter controls the number of semi-open connections that can be queued.

To change this value, use a text editor to edit the /etc/sysctl.conf file:

 sudo nano /etc/sysctl.conf

Add or modify the following line:

 <code>net.ipv4.tcp_max_syn_backlog = 4096</code>

You can replace 4096 with a larger value as you want.

To apply the changes, run the following command:

 sudo sysctl -p

2. Increase the number of file descriptors

The number of file descriptors determines how many connections the system can handle.

To increase this limit, open the /etc/security/limits.conf file:

 sudo nano /etc/security/limits.conf

Add the following lines at the end of the file:

 <code>* soft nofile 100000 * hard nofile 100000</code>

This will set the soft and hard limits for the maximum open file to 100,000 . You can adjust this number as you want.

3. Update system-wide file descriptor restrictions

In addition to user-specific restrictions, you can also increase the system-wide limits for file descriptors in /etc/sysctl.conf file.

 sudo nano /etc/sysctl.conf

Add or modify the following line:

 <code>fs.file-max = 100000</code>

Save and close the file, and apply the changes:

 sudo sysctl -p

Verify TCP connection restrictions in Linux

To ensure that the changes have been applied successfully, use the following command:

 sysctl net.ipv4.tcp_max_syn_backlog
cat /proc/sys/fs/file-max
ulimit -n

Other configurations (optional)

If you want to further fine-tune your network settings, you can adjust other parameters in the /etc/sysctl.conf file.

Here are some useful settings:

tcp_fin_timeout : Reduces the time the connection is in the FIN-WAIT-2 state, allowing faster reuse of the connection.

 <code>net.ipv4.tcp_fin_timeout = 15</code>

tcp_tw_reuse : Reusing the TIME-WAIT socket for a new connection can improve connection processing capabilities.

 <code>net.ipv4.tcp_tw_reuse = 1</code>

tcp_max_orphans : Increase the maximum number of masterless TCP sockets. This is very helpful for high load systems.

 <code>net.ipv4.tcp_max_orphans = 8192</code>

After making any other changes, remember to apply them using the following command:

 sudo sysctl -p

in conclusion

By following these steps, you can successfully increase the maximum number of TCP/IP connections in your Linux system, which will help your server handle more concurrent connections, thereby improving performance and user experience.

Always monitor server performance and adjust these settings as needed to maintain optimal operation.

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