tcp-ping-port

A simple TCP ping utility to ping a port of an IP or domain.

Table of contents

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• Benefits
• Installation
• How to use
• Dependencies
• API
• Testing

Benefits

---

Following are the pros and cons of this package compared to the regular ping

Pros

• Can be used with Amazon Lambda functions and Aazure functions.
  Regular ping uses ICMP protocol which is not permitted by AWS/Azure functions
• TCP packets have higher priorty than ICMP packets
• It can ping a particular port
• It can work even if ICMP is disabled

Cons

• Higher data usage

  Protocol	Send (B))	Receive (B)	Total (B)	Data saving
  TCP	228	126	354	0%
  ICMP	98	98	196	45%

  The numbers are based on data reported by Wireshark

  TCP Ping

  No.	Time	Source	Destination	Protocol	Length	Info
  1	0.000000	x.x.x.x	y.y.y.y	DNS	70	Standard query 0xfe55 A google.com
  2	0.000393	y.y.y.y	x.x.x.x	DNS	86	Standard query response 0xfe55 A google.com A 172.217.165.14
  3	0.001364	x.x.x.x	172.217.165.14	TCP	66	49985 → 80 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 WS=256 SACK_PERM=1
  4	0.012339	172.217.165.14	x.x.x.x	TCP	66	80 → 49985 [SYN, ACK] Seq=0 Ack=1 Win=65535 Len=0 MSS=1430 SACK_PERM=1 WS=256
  5	0.012412	x.x.x.x	172.217.165.14	TCP	54	49985 → 80 [ACK] Seq=1 Ack=1 Win=262912 Len=0
  6	0.013110	x.x.x.x	172.217.165.14	TCP	54	49985 → 80 [FIN, ACK] Seq=1 Ack=1 Win=262912 Len=0
  7	0.024927	172.217.165.14	x.x.x.x	TCP	60	80 → 49985 [FIN, ACK] Seq=1 Ack=2 Win=65536 Len=0
  8	0.024987	x.x.x.x	172.217.165.14	TCP	54	49985 → 80 [ACK] Seq=2 Ack=2 Win=262912 Len=0

  ICMP ping

  No.	Time	Source	Destination	Protocol	Length	Info
  1	0.000000	x.x.x.x	y.y.y.y	DNS	70	Standard query 0xff9e A google.com
  2	0.003286	y.y.y.y	x.x.x.x	DNS	86	Standard query response 0xff9e A google.com A 172.217.165.14
  3	0.040291	x.x.x.x	172.217.165.14	ICMP	98	Echo (ping) request id=0x0279, seq=1/256, ttl=128 (reply in 6)
  4	0.064258	172.217.165.14	x.x.x.x	ICMP	98	Echo (ping) reply id=0x0279, seq=1/256, ttl=112 (request in 5)

  NOTE: The first 2 DNS resolution calls are same in both cases for IPv4 and are not included in the total data usagage.

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Installation

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$ npm install tcp-ping-port --save

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How to use

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Simple examples

const { tcpPingPort } = require("tcp-ping-port")

tcpPingPort("google.com").then(({online}) => {
    // ....
})

With additional options

const { tcpPingPort } = require("tcp-ping-port")
const dns = require('dns')
const options = { 
    socketTimeout: 11000, 
    dnsTimeout: 10000,
    dnsServers: '8.8.8.8',  // google DNS
}
tcpPingPort("google.com", 80, options).then(({online, ping}) => {
    // ....
})

Check if host is offline

const { tcpPingPort } = require("tcp-ping-port")

tcpPingPort("google.com").then(result => {
    if (!result.online && result.error.code === 'TCPPINGTIMEOUT') {
        // your code when host is not accessible....
    }
})

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Dependencies

• dns-fast-resolver - to resolve multiple domains at the same time and to handle any errors while resolving the domain name. Also, to skip the whole dns resolution if host name is an IP address.
• lodash
• maketype

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API

tcpPingPort(hostname[, port, options, resolver])

Attemps to open and close TCP connection

• hostname <string> Host name or an IP address to try to connect to

• port <number> Port number

• options <Object> Socket and Resolver options

  • socketTimeout <integer> Number of milliseconds to wait before the resolving request is canceled. Default value 4000 (4s).
  • dnsTimeout <integer> Number of milliseconds to wait before the resolving request is canceled. Default value 4000 (4s).
    Usefull for rare cases when hostnames may need more than default 4 seconds to be resolved.
  • dnsServers <string[]> Array of RFC 5952 formatted addresses. (Example: ['4.4.4.4', '[2001:4860:4860::8888]', '4.4.4.4:1053', '[2001:4860:4860::8888]:1053'])

• returns <Promise<Result>> Promise that will return online status of host.

  • Result properties
    • online - indicates if host is online
      • True - when host is online and TCP connection is successfully opened and closed
      • False - when host name is not resolved or it failed to open a TCP connection. Check Result.error for details.
    • ping - returns duration (latency) of the ping in milliseconds.
    • error - returns error causing the host to be flagged as offline. Useful in verifying the host is offline.
    • host - hostname
    • port - port
    • ip - DNS Resolved IP address of the hostname

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Testing

Run all tests

$ npm test

Run individual test ping "google.com:80"

$ npm run unit-test -- --grep "google.com:80"

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