Networking with ping and wget—what they do, when to use them, and the flags you’ll actually need.

1) ping — “Is it reachable? How fast is it?”

What it does: sends ICMP Echo Request packets and waits for Echo Reply. Great for checking reachability, latency (ms), and packet loss.

Note: Some hosts block ICMP, so ping may fail even if a website works.

Quick starts

ping google.com                 # continuous pings until Ctrl+C

ping -c 5 google.com            # send 5 pings then stop

ping -4 example.com             # force IPv4

ping -6 example.com             # force IPv6

Useful options (Linux iputils ping)

·         -c N → send N packets (e.g., -c 5)

·         -i S → interval between pings (sec) (default 1s)

·         -s BYTES → payload size (e.g., -s 1400)

·         -W S → per-reply timeout (seconds)

·         -w S → overall deadline; exit after S seconds

·         -t N → set TTL (time-to-live) value

·         -q → quiet (summary only)

·         -n → numeric output (skip DNS)

Examples:

ping -c 5 -i 0.2 -W 2 8.8.8.8       # 5 pings, 200ms apart, 2s timeout each

ping -c 3 -s 1400 -W 1 example.com  # test with larger payload

Read the output

·         Per line: time=xx.x ms is round-trip latency.

·         Summary: packet loss, min/avg/max/mdev (mean deviation ≈ jitter).

Exit codes (good for scripts)

·         0 = at least one reply received

·         1 = no replies

·         2 = error (e.g., bad args)

Common issues

·         unknown host → DNS problem; try ping 8.8.8.8 (IP direct).

·         100% loss to a site that loads in browser → ICMP likely blocked.

·         High time or variable (jitter) → congestion or Wi-Fi issues.

·         High wa (I/O wait) in top while pinging? Disk is the bottleneck, not network.

2) wget — “Download this (and maybe a whole site)”

What it does: non-interactive downloader for HTTP/HTTPS/FTP. Perfect for scripts and large/long downloads.

Quick starts

wget https://example.com/file.zip        # save using remote filename

wget -O notes.pdf https://site/notes     # save as a specific name

wget -c https://site/big.iso             # resume a partial download

Everyday options

·         -O FILE → write to this filename

·         -c → continue (resume) if file exists

·         --limit-rate=200k → throttle speed

·         -q / -nv / -v → quiet / less chatty / verbose

·         --show-progress → progress bar (when not quiet)

·         --timeout=SECONDS / --tries=N → robustness on flaky nets

Website / directory downloads

·         -r → recursive

·         -np → no parent (don’t climb up)

·         -l N → recursion depth

·         -m → mirror mode (same as -r -N -l inf --no-remove-listing)

·         -N → timestamping (download only if newer)

·         -e robots=off → ignore robots.txt (use responsibly!)

Example: mirror a docs section (shallow):

wget -r -np -l 2 -k -p https://example.com/docs/

# -k: convert links for local viewing; -p: get page requisites (CSS/imgs)

Auth, headers, and cookies

wget --user=alice --password=secret https://site/private/file

wget --header="Authorization: Bearer <TOKEN>" https://api.example.com/data.json

wget --save-cookies cookies.txt --keep-session-cookies URL

wget --load-cookies cookies.txt URL

Handling redirects & content names

wget --content-disposition https://example.com/download?id=123

# use server's suggested filename from the Content-Disposition header

Background & lists

wget -b URL                            # run in background (logs to wget-log)

wget -i urls.txt                       # download all URLs from a file

Proxies (lab/campus networks)

export http_proxy=http://proxy:3128

export https_proxy=http://proxy:3128

wget https://example.com

SSL/TLS notes

·         Certificate errors? Prefer fixing CA/cert.

·         --no-check-certificate disables validation (avoid unless you truly must, and never in production scripts).

3) When to use which?

Need to test actual HTTP (status codes/headers)? curl -I https://example.com is better for protocol-level checks.

4) Mini-labs (25–35 minutes)

Lab A: Reachability & latency

ping -c 5 google.com

ping -c 5 8.8.8.8

ping -c 5 -4 example.com

ping -c 5 -6 example.com

# Compare loss/avg time; note differences IPv4 vs IPv6 if any.

Lab B: Timeouts & packet size

ping -c 5 -W 1 -s 1200 example.com

# Try increasing -s; observe if loss increases (some paths drop large ICMP).

Lab C: Robust file downloads

wget https://speed.hetzner.de/100MB.bin -O test.bin

# interrupt (Ctrl+C), then:

wget -c https://speed.hetzner.de/100MB.bin -O test.bin   # resumes

Lab D: Batch downloads

printf "%s\n" \

  https://example.org/a.pdf \

  https://example.org/b.pdf > urls.txt

wget -i urls.txt -P ~/Downloads/papers

Lab E: Shallow mirror (offline view)

wget -r -np -l 1 -k -p https://example.com/docs/

# open the saved index.html in a browser and browse locally

5) Troubleshooting quickies

ping

·         unknown host → DNS issue; check /etc/resolv.conf or try IP.

·         Only IPv6 fails → ISP/router may lack IPv6; use -4.

·         Packet loss spikes → Wi-Fi interference; move closer/switch band.

·         Consistently high latency → overloaded link or distant server.

wget

·         404 Not Found / 403 Forbidden → wrong URL or access control.

·         certificate verify failed → clock wrong or missing CA; fix CA/clock rather than --no-check-certificate.

·         Stalls midway → add --tries=10 --timeout=15 --continue --limit-rate=500k.

Exam-ready bullets

·         ping tests ICMP reachability and measures latency/jitter/loss. Key flags: -c, -i, -W, -w, -4/-6, -s, -n. Exit codes: 0 some replies, 1 none, 2 error.

·         wget downloads via HTTP/HTTPS/FTP; resume with -c, name with -O, rate-limit with --limit-rate, mirror with -r -np -k -p/-m, use headers/auth/cookies when needed.

·         ping can fail even when web works (ICMP blocked). For HTTP behavior, prefer curl -I.

Want this as a printable 2-page handout with a one-glance flag table? I can format and share it.