網路參考
在一個分頁式工具中查看 DNS 記錄、常用連接埠、HTTP 狀態碼和通訊協定標頭四類參考。
DNS 記錄參考
互動式DNS 記錄類型的互動式參考工具。
- 指令產生器
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
連接埠參考
IANA 官方包含安全風險等級的 IANA 連接埠資料庫。
- 安全性標記
- 純用戶端運行
Search Ports
Quick Stats
Total Ports
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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 狀態碼參考
RFC 9110可搜尋的標準 HTTP 狀態碼參考，附上用途與快取指引。
- 可搜尋
- 僅在瀏覽器中處理
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.
協定標頭參考
瀏覽 HTTP/SMTP/DNS 協定標頭。
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) |