centos下的nc是“netcat”的简称，是一个网络工具，可以用于端口扫描、文件传输等，nc也可以实现任意TCP和UDP端口的侦听，可以利用“yum install nc -y”命令进行安装。
本文操作环境：centos 7系统、Dell G3电脑。
centos下什么是nc
nc是netcat工具的简称，一个网络工具，可以用来端口扫描、文件传输等功能。
centos上面安装也很简单：
yum install nc -y
nc常用功能
实现任意TCP/UDP端口的侦听，nc可以作为server以TCP或UDP方式侦听指定端口
端口的扫描，nc可以作为client发起TCP或UDP连接
机器之间传输文件
机器之间网络测速
一般nc只用来做TCP/UDP协议的端口测试，其它功能少用！
nc帮助说明
CentOS Linux 7.9.2009
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CentOS Linux 7.9.2009是传统CentOS Linux 7的最后主要版本，也是很多企业历史服务器中仍可能遇到的系统版本。它以稳定、兼容RHEL 7生态、文档丰富和软件支持广泛著称，曾长期用于Web服务、数据库、虚拟化节点和企业内部业务系统。不过CentOS Linux 7已于2024年6月30日停止维护，现在继续使用会面临安全补丁缺失风险。该版本更适合旧业务迁移、历史环境恢复或离
# nc --help
Ncat 7.50 ( https://nmap.org/ncat )
Usage: ncat [options] [hostname] [port]
Options taking a time assume seconds. Append 'ms' for milliseconds,
's' for seconds, 'm' for minutes, or 'h' for hours (e.g. 500ms).
-4 Use IPv4 only
-6 Use IPv6 only
-U, --unixsock Use Unix domain sockets only
-C, --crlf Use CRLF for EOL sequence
-c, --sh-exec <command> Executes the given command via /bin/sh
-e, --exec <command> Executes the given command
--lua-exec <filename> Executes the given Lua script
-g hop1[,hop2,...] Loose source routing hop points (8 max)
-G <n> Loose source routing hop pointer (4, 8, 12, ...)
-m, --max-conns <n> Maximum <n> simultaneous connections
-h, --help Display this help screen
-d, --delay <time> Wait between read/writes
-o, --output <filename> Dump session data to a file
-x, --hex-dump <filename> Dump session data as hex to a file
-i, --idle-timeout <time> Idle read/write timeout
-p, --source-port port Specify source port to use
-s, --source addr Specify source address to use (doesn't affect -l)
-l, --listen Bind and listen for incoming connections
-k, --keep-open Accept multiple connections in listen mode
-n, --nodns Do not resolve hostnames via DNS
-t, --telnet Answer Telnet negotiations
-u, --udp Use UDP instead of default TCP
--sctp Use SCTP instead of default TCP
-v, --verbose Set verbosity level (can be used several times)
-w, --wait <time> Connect timeout
-z Zero-I/O mode, report connection status only
--append-output Append rather than clobber specified output files
--send-only Only send data, ignoring received; quit on EOF
--recv-only Only receive data, never send anything
--allow Allow only given hosts to connect to Ncat
--allowfile A file of hosts allowed to connect to Ncat
--deny Deny given hosts from connecting to Ncat
--denyfile A file of hosts denied from connecting to Ncat
--broker Enable Ncat's connection brokering mode
--chat Start a simple Ncat chat server
--proxy <addr> Specify address of host to proxy through
--proxy-type <type> Specify proxy type ("http" or "socks4" or "socks5")
--proxy-auth <auth> Authenticate with HTTP or SOCKS proxy server
--ssl Connect or listen with SSL
--ssl-cert Specify SSL certificate file (PEM) for listening
--ssl-key Specify SSL private key (PEM) for listening
--ssl-verify Verify trust and domain name of certificates
--ssl-trustfile PEM file containing trusted SSL certificates
--ssl-ciphers Cipherlist containing SSL ciphers to use
--version Display Ncat's version information and exit</auth></type></addr></time></time></filename></filename></time></n></n></n></filename></command></command>
nc常用案例
TCP监听测试
nc可作为server端192.168.10.11启动一个tcp的监听
nc -l 80
客户端测试方法：直接telnet该机器ip+端口
telnet 192.168.10.11 80
或：nmap 192.168.10.11 -p 80
UDP监听测试
nc作为server端启动一个udp的监听
nc -lu 80
通过netstat可以看到udp协议已经监听：
> # netstat -tunlp Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name udp 0 0 0.0.0.0:80 0.0.0.0:* 15401/nc
推荐教程：《centos教程》
