# zmap > Fast, open-source network scanner for Internet-wide surveys. > More information: . - Scan a subnet or full IPv4 space for a specific TCP port (default: 80): `zmap {{SUBNETS}} {{[-p|--target-ports]}} {{port}}` - Scan specific ports or port ranges across a subnet: `zmap {{[-p|--target-ports]}} {{port1,port2-port3,...}} {{SUBNETS}}` - Output results to a CSV file with custom fields: `zmap {{[-o|--output-file]}} {{path/to/output_file.csv}} {{[-f|--output-fields]}} "{{saddr,daddr,sport,dport}}" {{SUBNETS}}` - Limit the scan rate to a specific number of packets per second: `zmap {{[-r|--rate]}} {{packets_per_second}} {{SUBNETS}}` - Perform a dry run without sending packets: `zmap {{[-d|--dryrun]}} {{SUBNETS}}` - Exclude subnets using a blocklist file in CIDR notation: `zmap {{[-b|--blocklist-file]}} {{path/to/blocklist.txt}} {{SUBNETS}}` - Set a specific source IP for scan packets: `zmap {{[-S|--source-ip]}} {{source_ip}} {{SUBNETS}}` - Cap the number/percentage of targets to probe (e.g. 1000 IP/port pairs): `zmap {{[-n|--max-targets]}} {{1000}} {{SUBNETS}} {{[-p|--target-ports]}} {{port1,port2-port3}}`