I need millions of tcp flows

[liw71]

hey, at work, I need to create millions of TCP flows in parallel. is this right tool? thank you in advance.
Wei

[d0xeon]

Short answer: probably not — RustScan is a port scanner, not a traffic/flow generator. It fires a burst of short-lived TCP connect() probes across a host's port range to find which ports are open (then usually hands off to nmap). It is built to discover open ports fast, not to sustain millions of TCP flows.

The right tool depends on what "flows" means for you:

Load / concurrency testing (many simultaneous TCP connections against a server) — tcpkali is purpose-built (multi-core TCP/WebSocket load generator); wrk / hey / vegeta for HTTP; iperf3 for raw throughput.

High-rate packet/flow generation (stress a firewall/IDS/NIC) — Cisco TRex, Ostinato, or pktgen-DPDK.

Generating TCP flow records (NetFlow/IPFIX, e.g. for a dataset / ML / IDS work) — replay real captures with tcpreplay, extract flows from pcaps with Zeek / nfdump / CICFlowMeter, or export with softflowd.

If you can say whether you need live connections, raw packet throughput, or flow records on disk, folks here can point you at the most specific option.