一、命令简介
Netcat的简称nc，是一款被誉为网络界瑞士军刀的强大网络工具。实际上，Linux系统中的命令是ncat。nc命令只是一个指向ncat的软链接。nc命令的主要作用如下：
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
nc如果找不到nc命令可以使用yum install -y nc安装，其中centos6系统安装的是nc-1.84-24.el6.x86_64，centos7安装的是nmap-ncat-6.40-19.el7.x86_64。
二、使用示例
1、验证服务器端口是否通如下验证172.16.7.78服务器的80端口通，81端口不通。
首先在文件接收终端test2机器上激活nc监听
然后在文件发送终端test1机器上发送文件
在test2上检查文件是否已成功接收
test1主机上启动nc监听，ctrl+C中断通信。
test2上连接监听，ctrl+C中断通信。
端口扫描，通的端口返回succeeded，不通的端口返回refused。此扫描基于nc-1.84-24.el6.x86_64。
[root@test1 /]# nc -v -w 1 172.16.7.78 -z 22-81
Connection to 172.16.7.78 22 port [tcp/ssh] succeeded!
nc: connect to 172.16.7.78 port 23 (tcp) fAIled: Connection refused
nc: connect to 172.16.7.78 port 24 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 25 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 26 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 27 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 28 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 29 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 30 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 31 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 32 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 33 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 34 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 35 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 36 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 37 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 38 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 39 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 40 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 41 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 42 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 43 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 44 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 45 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 46 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 47 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 48 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 49 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 50 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 51 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 52 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 53 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 54 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 55 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 56 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 57 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 58 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 59 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 60 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 61 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 62 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 63 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 64 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 65 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 66 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 67 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 68 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 69 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 70 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 71 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 72 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 73 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 74 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 75 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 76 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 77 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 78 (tcp) failed: Connection refused
nc: connect to 172.16.7.78 port 79 (tcp) failed: Connection refused
Connection to 172.16.7.78 80 port [tcp/http] succeeded!
nc: connect to 172.16.7.78 port 81 (tcp) failed: Connection refused 5、验证UDP端口[root@test1 ~]# nc -uvz 192.168.0.125 111
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to 192.168.0.125:111.
Ncat: UDP packet sent successfully
Ncat: 1 bytes sent, 0 bytes received in 2.04 seconds. 6、测速网速测速网速需要结合dstat命令查看。
安装dstat命令
[root@test1 ~]# yum install -y dstat
[root@test2 ~]# yum install -y dstattest1主机上监听端口
[root@test1 ~]# nc -l 33333 >/dev/null
test2主机上发送数据，全0数据
[root@test2 ~]# nc 192.168.0.124 33333 </dev/zero
查看流量
[root@test1 ~]# dstat
[root@test2 ~]# dstat
三、使用语法及参数说明
1、使用语法用法：ncat [options] [hostname] [port]
2、参数说明 参数 参数说明 -4 Use IPv4 only -6 Use IPv6 only -U, –unixsock 仅使用Unix域套接字 -C, –crlf 将crlf用于EOL序列 -c, –sh-exec <command> 通过/bin/sh执行给定的命令 -e, –exec <command> 执行给定的命令 –lua-exec <filename> 执行给定的lua脚本 -g hop1[,hop2,…] 松散源路由跃点（最多8个） -G <n> 松散源路由跃点指针（4，8，12，…） -m, –max-conns <n> 最大同时连接数 -h, –help 帮助显示此帮助屏幕 -d, –delay <time> 读/写之间的延迟 -o, –output <filename> 将会话数据转储到文件 -x, –hex-dump <filename> 将会话数据作为十六进制转储到文件 -i, –idle-timeout <time> 空闲读/写超时 -p, –source-port port 指定要使用的源端口 -s, –source addr 指定要使用的源地址（不影响-l） -l, –listen 绑定并侦听传入连接 -k, –keep-open 在侦听模式下接受多个连接 -n, –nodns 不通过DNS解析主机名 -t, –telnet 应答telnet协商 -u, –udp 使用udp而不是默认TCP –sctp 使用sctp而不是默认的TCP -v, –verbose 设置详细级别（可以多次使用） -w, –wait <time> 连接超时时间，单位秒 -z 仅报告连接状态 –append-output 追加而不是重击指定的输出文件 –send-only 忽略接收；退出EOF –recv-only 从不发送任何东西 –allow 给定主机连接到Ncat –allowfile 允许连接到Ncat的主机的文件 –deny 给定主机连接到Ncat –denyfile 拒绝连接到Ncat的主机文件 –broker 启用Ncat的连接代理模式 –chat 开始一个简单的Ncat聊天服务器 –proxy <addr[:port]> 指定要通过代理的主机地址 –proxy-type <type> 指定代理类型（“http”或“socks4”或“socks5”） –proxy-auth <auth> 通过HTTP或SOCKS代理服务器进行身份验证 –ssl 使用ssl连接或侦听 –ssl-cert 指定用于侦听的ssl证书文件（PEM） –ssl-key 指定用于侦听的ssl私钥（PEM） –ssl-verify 证书的信任和域名 –ssl-trustfile 包含可信ssl证书的PEM文件 –ssl-ciphers Cipherlist包含要使用的ssl密码 –version 查看命令版本
暂无评论内容