The network connection status of Japanese servers is a key tool that operations and maintenance personnel must constantly monitor. In both Linux and Windows environments, the Netstat command is one of the most commonly used network debugging tools. This article will comprehensively explain the Netstat command's usage, including basic beginners and advanced applications, along with detailed parameter descriptions, application scenarios, and solutions to common problems, focusing on the network environment of Japanese servers. This article aims to help businesses and individual users better utilize this tool for network management.

Basic Netstat Command Usage:

The Netstat command is a native operating system network tool used to display information such as current network connections, routing tables, and interface status.

1. Basic Syntax

netstat [parameters]

2. Common Parameters

-a: Displays all connections and listening ports.

-n: Displays addresses and port numbers in numeric form, rather than resolved to domain names.

-t: Displays only TCP connections.

-u: Displays only UDP connections.

-p: Displays the process PID and program name.

-l: Displays only listening connections.

-s: Displays network statistics.

3. Examples

# View all connections
netstat -an

# View all listening ports
netstat -lnp

# View TCP connections
netstat -ant

# View UDP connections
netstat -anu

Practical Netstat Use Cases in a Japanese Server Environment:

1. Checking Port Usage

Suppose you have deployed an Nginx website on a Japanese server and are experiencing a common startup error: "Address already in use."

You can use:

netstat -tlnp | grep 80

This allows you to quickly identify the process occupying a port and avoid repeated restarts.

2. Monitor external connection sources

Japanese servers are often used as independent cross-border e-commerce websites and may be vulnerable to malicious scraping or attacks.

netstat -ant | grep ESTABLISHED

The results show which IP addresses are currently connected to the server and whether there are a large number of unusual IP requests.

3. Analyze the connection status

Use the following command:

netstat -ant | awk '{print $6}' | sort | uniq -c | sort -n

You can count the number of different connection states on the server (such as ESTABLISHED, TIME_WAIT, and CLOSE_WAIT). If you notice an excessive accumulation of TIME_WAIT sessions, this indicates a short connection problem on the server and requires optimizing kernel parameters (such as tcp_tw_reuse).

4. Check UDP Services

Japanese servers often use the UDP protocol for game proxy or DNS services.

netstat -anu

You can check the UDP port monitoring status to ensure the service is operating normally.

5. Interact with the firewall

After identifying the attack source, you can use the firewall to block the IP address:

iptables -A INPUT -s 192.168.1.100 -j DROP

This type of operation is particularly common on Japanese servers, as their outbound bandwidth is frequently consumed by DDoS attacks.

Combining Netstat with other commands:

1. Combining with grep

netstat -ant | grep 443

Quickly locate the HTTPS port connection status.

2. Combine with wc

netstat -ant | grep ESTABLISHED | wc -l

Counts the number of currently established connections.

3. Combined with lsof

lsof -i:80 is similar to netstat -tlnp in that both show port usage, but lsof provides more detailed information.

4. Comparison with the ss Command

In some newer Linux versions, the ss command is faster and can replace netstat, but netstat remains the most common and versatile tool.

Advanced Netstat Usage for Japanese Servers:

1. Viewing the Routing Table

netstat -r

This can be used to confirm whether Japanese servers are correctly routing traffic to overseas users, avoiding routing loops or configuration errors.

2. Network Interface Statistics

netstat -i

Displays the traffic sent and received by each server network card, useful for troubleshooting bandwidth bottlenecks.

3. Protocol Statistics

netstat -s

View detailed statistics for protocols like TCP, UDP, and ICMP to help determine packet loss rates or abnormal connections.

Netstat considerations for Japanese server maintenance:

1. Security: Netstat output includes process IDs, so avoid exposing them directly to ordinary users during maintenance.

2. Performance impact: In high-concurrency scenarios, Netstat output can be very large. Use filtering commands to prevent this from affecting troubleshooting efficiency.

3. Logging: It is recommended to run Netstat regularly on Japanese servers and save logs for post-incident attack detection.

4. Integration with monitoring systems: By integrating with monitoring tools like Zabbix and Prometheus, Netstat results can be visualized for continuous monitoring.

As a classic network debugging tool, Netstat plays an irreplaceable role in Japanese server maintenance. Whether checking port usage, troubleshooting abnormal connections, or performing network status statistics, Netstat quickly provides critical information. For companies that rely on Japanese servers for cross-border e-commerce, video, gaming, finance, and other businesses, mastering the use of Netstat can not only improve operation and maintenance efficiency, but also enable quick response when encountering attacks or failures, ensuring stable business operations.