Bandwidth Measurement using netcat on Linux
There are various implementations. I am using nmap-ncat on rockOS 8 on both hosts.
Netcat's using TCP by default and this test is not limited by disk I/O from what I understood. That said, it is not the best solution, but it is a great 'quick and dirty' method. Additionally, there is no encryption overhead and no compression involved.
Important: Please use with caution. You can lose access to a host while performing the test.
- Server / Receiver:
nc -k -v -l 33333 > /dev/null
-
-k
# keeps listening after connection ends (might not be available e.g. gnu-netcat) -
-v
# verbose output -
-l 33333
# listen on port 33333 (default TCP) -
> /dev/null
# send incoming data into the void to avoid disk I/O - Client / Sender:
dd if=/dev/zero bs=500M count=1 | nc -v 192.0.2.5 33333
-
dd
# convert/copy files -
if=/dev/zero
# read from file, only zeros in this case -
bs=500M
# sets the data-/ blocksize, 500 Mibibytes, use500MB
for Megabytes, -
count=1
# set the maximum number of blocks, just leave it at1
-
|
# 'pipes' all data to the next command -
nc
# netcat command -
-v
# set a more verbose output -
192.0.2.5
# set destination server IP -
33333
# set destination port
Result on the client side
[user@test-rocky-01 ~]$ dd if=/dev/zero bs=500M count=1 | nc -v 192.0.2.5 33333 Ncat: Version 7.92 ( https://nmap.org/ncat ) Ncat: Connected to 192.0.2.5:33333. 1+0 records in 1+0 records out 524288000 bytes (524 MB, 500 MiB) copied, 19.6253 s, 26.7 MB/s Ncat: 524288000 bytes sent, 0 bytes received in 19.71 seconds.
Result on the server side
[user@test-rocky-02 ~]$ nc -k -v -l 33333 > /dev/null Ncat: Version 7.92 ( https://nmap.org/ncat ) Ncat: Listening on :::33333 Ncat: Listening on 0.0.0.0:33333 Ncat: Connection from 198.51.100.19. Ncat: Connection from 198.51.100.19:42822. Ncat: Connection from 198.51.100.19. Ncat: Connection from 198.51.100.19:43088. [...]
Side note: It is recommended to test both directions.
Additional options
Side note: For security reasons on most systems you need higher permissions to use ports in the range of 0-1023 (reserved port range).
[user@test-rocky-02 ~]$ nc -k -v -l 444 > /dev/null Ncat: Version 7.92 ( https://nmap.org/ncat ) Ncat: bind to :::444: Permission denied. QUITTING.
- Specify source interface/IP:
-s 10.20.10.8
- Specify source port:
-
-p 45454
# on the client obviously - Tip: changing the source port with every run to find a specific run faster in a packet capture
- Using UDP instead of TCP:
-
-u
# must be used on both hosts and might not be compatible with other options
Troubleshooting
Large transfer / longer test
[user@test-rocky-01 ~]$ dd if=/dev/zero bs=4G count=1 | nc -p 5555 -v 192.0.2.5 33333
dd: memory exhausted by input buffer of size 4294967296 bytes (4.0 GiB)
You are limited by your RAM when you want to send more data. You can decrease bs=4G
to bs=1G
, and increase the counter count=1
to 4
to transfer 4GiB of data.
Connection refused
Ncat: Connection refused.
Ncat: TIMEOUT.
Make sure: - that the netcat server is running - double-check the destination host and port of the command - make sure that you can reach the destination over this port - network firewalls - routing - check both host firewalls and make sure the inbound and outbound traffic is allowed
Caution
As mentioned before, you can lose access to your hosts. Additionally, please announce tests to your network and security team as you can disrupt a productive network or trigger some kind of IDS system in place.
E-Mail
hello
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