Description
Accept a computed 16-bit checksum and replace zero with 65535; return every other word unchanged.
A UDP checksum word and the UDP length field serve different purposes: one detects corruption, while the other counts header plus payload bytes. IP version affects checksum policy.
Accept a computed 16-bit checksum and replace zero with 65535; return every other word unchanged.
When to use this tool
Use UDP Checksum Negative Zero Transmit Word when you need to inspect a supplied UDP length or checksum convention.
How to use the tool and how it works
- Enter computedChecksum. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read transmittedChecksum. Use the output convention below.
Accept a computed 16-bit checksum and replace zero with 65535; return every other word unchanged.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| computedChecksum | Computed Checksum | Required. Safe integer; minimum 0; maximum 65535. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| transmittedChecksum | Transmitted Checksum | Required. Safe integer. |
{
"input": {
"computedChecksum": 0
},
"output": {
"transmittedChecksum": 65535
}
}Limitations and assumptions
- This maps a completed checksum for transmission; it does not compute the checksum or validate a packet.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use packet capture and a complete datagram checksum verifier for end-to-end validation.
References
Similar or alternative tools
- Network: UDP Zero Checksum Version Policy
Check IP version 4 or 6 and a 16-bit checksum.
- IPv4 Header Checksum Word Contribution
Combine high and low octets as high × 256 + low to obtain a 16-bit network-order word.