Man pages › Compared with Linux and the BSDs

`nc(1)` on Solnix vs Linux and the BSDs

On Solnix, nc is the illumos nc at /usr/bin/nc. It does plain TCP, UDP and Unix-domain sockets, with SOCKS/HTTP proxy support, but has no TLS and no -N. The biggest trap for BSD users: Solnix allows -l together with -p to set the listen port, while FreeBSD, OpenBSD and NetBSD reject that combination.

The manual pages

Solnix: nc(1) from pkgs.solnix.illumos-world-man · illumos.org
FreeBSD: nc(1) 15.1-RELEASE
OpenBSD: nc(1) 8.0
NetBSD: nc(1) 11.0

What Solnix runs

A default Solnix system runs the illumos nc at /usr/bin/nc. No other variants are shipped. The Solnix page documents -B (bypass IPsec policy) and -S (TCP MD5, which needs a security association made with tcpkey(8)).

Differences

Compared with	Topic	What differs
FreeBSD, OpenBSD, NetBSD	`-p` with `-l`	On Solnix, `-p` port with `-l` sets the listen port (allowed only if no port operand is given). On FreeBSD, OpenBSD and NetBSD, using `-p` with `-l` is an error, because `-p` there means source port only. Source: Solnix nc(1) SYNOPSIS (nc -l ... -p port), -p; FreeBSD nc(1) -p, -l; OpenBSD nc(1) -p, -l; NetBSD nc(1) -p, -l
OpenBSD, NetBSD	TLS	OpenBSD and NetBSD nc have `-c` to use TLS, plus `-C`, `-K`, `-e`, `-H`, `-R` and `-o` for certificates and verification. The Solnix page documents none of these, so Solnix nc has no TLS option. The FreeBSD page has none either. Source: OpenBSD nc(1) -c, -C, -K, -R; NetBSD nc(1) -c, -C, -K, -R; Solnix nc(1) OPTIONS
FreeBSD, OpenBSD, NetBSD	`-N` missing	Solnix has no `-N`. On the BSDs, `-N` calls shutdown(2) on the socket after EOF on input, which some servers need before they finish. On Solnix the manual documents no equivalent. Source: FreeBSD nc(1) -N; OpenBSD nc(1) -N; NetBSD nc(1) -N; Solnix nc(1) OPTIONS
FreeBSD, OpenBSD, NetBSD	`-F` (pass socket)	Solnix has no `-F`. On the BSDs, `-F` passes the first connected socket to stdout with sendmsg(2) and exits, for use with `-X` and ssh ProxyUseFdpass. Source: FreeBSD nc(1) -F; OpenBSD nc(1) -F; NetBSD nc(1) -F; Solnix nc(1) OPTIONS
FreeBSD	`-M` meaning and `-m`	Solnix `-M` sets the outgoing IPv4 TTL or IPv6 hop count. FreeBSD `-M` collects per-connection TCP statistics and prints them as JSON to stderr. FreeBSD documents no `-m`, which on Solnix sets a minimum received TTL. Source: Solnix nc(1) -M, -m; FreeBSD nc(1) SYNOPSIS, -M
FreeBSD, OpenBSD, NetBSD	`-T` keywords	Solnix `-T` accepts only lowdelay, throughput, reliability or a number from 0 to 255. The BSDs also accept critical, inetcontrol, netcontrol and DiffServ names (ef, af11 ... af43, cs0 ... cs7). OpenBSD and NetBSD also use `-T` for TLS options. Source: Solnix nc(1) -T; FreeBSD nc(1) -T; OpenBSD nc(1) -T; NetBSD nc(1) -T
FreeBSD, OpenBSD, NetBSD	Unix-domain sockets	Solnix documents `-U` with a stream socket only: its `-U` synopsis lists no `-u`, and the path is a single argument. FreeBSD, OpenBSD and NetBSD let `-u` select a datagram socket with `-U`, creating a temporary receiving socket in /tmp unless `-s` is given. Source: Solnix nc(1) SYNOPSIS (nc -U ...), -U; FreeBSD nc(1) -u, -s; NetBSD nc(1) -u; OpenBSD nc(1) -u
FreeBSD, OpenBSD, NetBSD	buffer sizes	Solnix has no `-I` or `-O`. On the BSDs, `-I` sets the TCP receive buffer size and `-O` the TCP send buffer size. Source: FreeBSD nc(1) -I, -O; OpenBSD nc(1) -I, -O; NetBSD nc(1) -I, -O; Solnix nc(1) OPTIONS
FreeBSD, OpenBSD	routing table	Solnix has no `-V`. FreeBSD and OpenBSD `-V` rtable select the routing table (FIB). OpenBSD also has `-W` recvlimit; FreeBSD also has `--sctp`, `--lb`, `--crlf`, `--tun` and `--no-tcpopt`. None of these are in the Solnix page. Source: FreeBSD nc(1) -V, --sctp, --lb, --crlf, --tun; OpenBSD nc(1) SYNOPSIS (-V, -W); Solnix nc(1) SYNOPSIS
FreeBSD	IPsec options	Solnix `-B` bypasses IPsec policy and sends cleartext. It needs the sys_ip_config privilege and fails with `-l` or `-U`. FreeBSD has no `-B`; it has `-e` and `-E` to require IPsec ESP. Source: Solnix nc(1) -B; FreeBSD nc(1) -E, -e
FreeBSD, OpenBSD, NetBSD	`-n` behaviour	Solnix `-n` limits hostname and port arguments to numeric values, and has no effect with `-U`. The BSD pages describe `-n` only as skipping DNS or service lookups (OpenBSD: an unresolvable name is an error). Source: Solnix nc(1) -n; FreeBSD nc(1) -n; OpenBSD nc(1) -n; NetBSD nc(1) -n

Standards

POSIX: nc is not a POSIX.1-2024 utility.

Writing portable scripts

Do not combine -l with -p in portable scripts: Solnix accepts it, while FreeBSD, OpenBSD and NetBSD reject it. Use the form nc -l [hostname] port, as in the Solnix page example nc -l 1234.
Do not rely on -N, -F, -c, -I, -O or -V. They are missing on Solnix or exist only on some BSDs, and -M means different things on FreeBSD and Solnix.

Every difference here is taken from the manual pages linked above: Solnix's published page, Linux (man-pages and the GNU and util-linux manuals), FreeBSD, OpenBSD and NetBSD. Each row names its source. Where a manual is silent, this page is too. Compiled 2026-10-26. Found a mistake? Mail hackers@lists.solnix.io.