网络参考
在一个选项卡式工具中查看 DNS 记录、常用端口、HTTP 状态码和协议头四类参考。
DNS 记录参考
交互式DNS 记录类型的交互式参考工具。
- 命令构建器
Description
Syntax Format
Example
Use Cases
TTL Recommendation
Security Notes
Command Builder
DKIM/SPF/DMARC use TXT records at specific subdomains.
dig example.com Anslookup -type=A example.comRoot Zone
The DNS hierarchy starts at the root (.) — 13 logical root name servers (a.root-servers.net through m.root-servers.net) handle queries for top-level domains.
Top-Level Domains (TLDs)
Managed by registries. Examples: .com, .org, .net (generic), .uk, .de (country-code), .app, .dev (new gTLDs). TLD servers delegate to authoritative name servers for each domain.
Authoritative Name Servers
These servers hold the actual DNS records for a domain. NS records point to them. They're the final authority for queries about that domain's records.
DNS Resolution Flow
- Stub resolver checks local cache
- Query recursive resolver (ISP or public DNS like 8.8.8.8)
- Recursive resolver queries root servers
- Root refers to TLD servers
- TLD refers to authoritative name servers
- Authoritative server returns the record
- Result is cached at each level
端口参考
IANA 官方包含安全风险等级的 IANA 端口数据库。
- 安全标记
- 仅限客户端
Search Ports
Quick Stats
Total Ports
0
Filtered
0
Results
| Port | Service | Protocol | Description | Risk |
|---|---|---|---|---|
| Start typing to search for ports... | ||||
Top 50 Most Common Ports
Port Number Ranges
| Range | Name | Description |
|---|---|---|
0-1023 | Well-Known | Reserved for system services (HTTP, SSH, etc.) |
1024-49151 | Registered | User-registered ports for applications |
49152-65535 | Dynamic/Private | Ephemeral ports for client connections |
High Risk Ports
| Port | Service | Risk |
|---|---|---|
21 | FTP | Unencrypted file transfers |
23 | Telnet | Plain text authentication |
25 | SMTP | Email spam relay risk |
53 | DNS | DDoS amplification attacks |
445 | SMB | Ransomware propagation |
3389 | RDP | Brute force attacks |
Security Best Practices
- Close unused ports: Reduce attack surface by disabling services you don't need
- Use firewalls: Implement network-level access controls
- Monitor traffic: Log connections to sensitive ports (22, 443, 3389)
- Prefer encrypted protocols: Use SSH (22) instead of Telnet (23), SFTP instead of FTP
- Change defaults: Consider non-standard ports for SSH/RDP (security through obscurity)
HTTP 状态码参考
RFC 9110可搜索的标准 HTTP 状态码参考，附带用途与缓存指南。
- 可搜索
- 仅在浏览器中处理
Search HTTP statuses
Search by code, phrase, class, description, or when-to-use guidance.
Status codes
Showing all HTTP status codes.
Class meanings
| Class | Meaning | Typical use |
|---|---|---|
1xx | Informational | Interim responses while a request continues. |
2xx | Successful | The request was received, understood, and accepted. |
3xx | Redirection | The client needs another request or cached representation. |
4xx | Client Error | The request has a client-side problem or cannot be fulfilled. |
5xx | Server Error | The server failed to fulfill an apparently valid request. |
Safety, idempotency, and caching
Status codes do not make a request safe or idempotent by themselves. Safety and idempotency come from the request method and application semantics.
RFC caching rules allow some responses to be reused by default, including common statuses such as 200, 203, 204, 206, 300, 301, 308, 404, 405, 410, 414, and 501. Other statuses generally need explicit cache headers.
协议头参考
浏览 HTTP/SMTP/DNS 协议头。
Field Details
Click on any field in the diagram to see details.
Ethernet II Header
14 bytesEthernet II
| Field | Size | Description |
|---|---|---|
| Destination MAC | 6 bytes | Target hardware address |
| Source MAC | 6 bytes | Sender hardware address |
| EtherType | 2 bytes | Protocol type (0x0800=IPv4, 0x86DD=IPv6) |
IPv4 Header
| Field | Size | Description |
|---|---|---|
| Version | 4 bits | IP version (4) |
| IHL | 4 bits | Header length in 32-bit words |
| TOS | 1 byte | Type of Service / DSCP |
| Total Length | 2 bytes | Total packet size |
| TTL | 1 byte | Time to Live (hop limit) |
| Protocol | 1 byte | Next protocol (6=TCP, 17=UDP) |
| Checksum | 2 bytes | Header checksum |
TCP Header
| Field | Size | Description |
|---|---|---|
| Source Port | 2 bytes | Sender port number |
| Dest Port | 2 bytes | Receiver port number |
| Seq Number | 4 bytes | Sequence number |
| Ack Number | 4 bytes | Acknowledgment number |
| Data Offset | 4 bits | Header length / 4 |
| Flags | 9 bits | NS,CWR,ECE,URG,ACK,PSH,RST,SYN,FIN |
| Window | 2 bytes | Receive window size |
Common EtherTypes
| Value | Protocol |
|---|---|
0x0800 | IPv4 |
0x0806 | ARP |
0x86DD | IPv6 |
0x8100 | VLAN (802.1Q) |