Various restrictions on the maximum number of connections to a high-concurrency socket under linux (remove IO limit)

Linux as a server system, when running high concurrent TCP programs, usually there will be a certain number of connections established after the connection can not be established

I am at work, testing high concurrent TCP program (GPS server-side program), multiple tests, found each connection established to 3800 or so, can no longer establish a TCP connection, the most total Internet search, reference: http://blog.csdn.net/guowake/article/ details/6615728 solve the connection limitations, recorded here, convenient for future work continue to use, although the reference blog post content a bit more, the content described in the text is not clear, but summarized down, as follows a few steps can be (i image, after this method is set, Test to establish a connection more than 8,000 when there are no errors):

• The first step, modify the /etc/security/limits.conf file, add the following line in the file (* Refer to the System user name), modify the Linux system on the user's number of open files soft limit and hard limit :

　　　　* Soft Nofile 20000

* Hard Nofile 20000

• In the second step, modify the /etc/pam.d/login file to add the following line to the file:

　　　　Session required/lib/security/pam_limits.so

　　　　If it is a 64bit system, it should be:
Session required/lib64/security/pam_limits.so

• In the third step, modify the /etc/sysctl.conf file to add the following line in the file (clear the original contents of the file) ( modify the network kernel restrictions on TCP connections ):

Net.ipv4.ip_local_port_range =1024x768 65535Net.core.rmem_max=16777216Net.core.wmem_max=16777216Net.ipv4.tcp_rmem=4096 87380 16777216Net.ipv4.tcp_wmem=4096 65536 16777216Net.ipv4.tcp_fin_timeout=Tennet.ipv4.tcp_tw_recycle=1Net.ipv4.tcp_timestamps=0net.ipv4.tcp_window_scaling=0Net.ipv4.tcp_sack=0Net.core.netdev_max_backlog=30000Net.ipv4.tcp_no_metrics_save=1Net.core.somaxconn=262144net.ipv4.tcp_syncookies=0Net.ipv4.tcp_max_orphans=262144Net.ipv4.tcp_max_syn_backlog=262144net.ipv4.tcp_synack_retries=2net.ipv4.tcp_syn_retries=2

• Fourth step, execute the following command (to make the above settings effective):

　　　　

/sbin/sysctl-p/etc/sysctl.conf/sbin/sysctl-w net.ipv4.route.flush=1

• Fifth step, execute the following command (Linux system optimized network must be high to allow the number of open files to support large concurrency, default 1024 is far from enough ):

　

65536 >>/etc/65536 >>/root/65536

• Sixth step, restart the machine.

Various restrictions on the maximum number of connections to a high-concurrency socket under linux (remove IO limit)