java 如何使用Java将自定义数据写入TCP数据包头选项字段？
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How to write custom data to the TCP packet header options field with Java?
提问by Matlabber
As it is defined (see: http://www.freesoft.org/CIE/Course/Section4/8.htm) the TCP header has an 'Options' field. There are a couple of options already defined (see: www.iana.org/assignments/tcp-parameters/) but I want to come up with my very own. (For experimenting/research.)
正如它所定义的（参见：http: //www.freesoft.org/CIE/Course/Section4/8.htm），TCP 标头有一个“选项”字段。已经定义了几个选项（参见：www.iana.org/assignments/tcp-parameters/）但我想提出我自己的。（用于实验/研究。）
How can I get Java to write (and then read) some custom data to the options field?
如何让 Java 向选项字段写入（然后读取）一些自定义数据？
Bonus question: if it cannot be done with Java. what kind of application can do this? (No, I don't really feel like messing with some kernel-level TCP/IP stack implementation, I want to keep it app level.)
额外的问题：如果它不能用 Java 完成。什么样的应用程序可以做到这一点？（不，我真的不想弄乱一些内核级 TCP/IP 堆栈实现，我想保持它的应用程序级别。）
Thanks!
谢谢！
回答by h3xStream
JNetPcap is a library that will allow you to change headers from low level layers including TCP. http://jnetpcap.com/node/29
JNetPcap 是一个库，允许您从低层（包括 TCP）更改标头。 http://jnetpcap.com/node/29
Here is a quick example:
这是一个快速示例：
byte[] pktBytes = FormatUtils.toByteArray("0015c672234c90e6ba92661608004500002d358c4000800600000a000b050a090028c26e270fb8b256e3a2009f785018faf01f550000746573740a");
JMemoryPacket packet = new JMemoryPacket(pktBytes);
packet.scan(Ethernet.ID); //Need to be done before doing any edits
//Editing Ip layer
Ip4 ip = packet.getHeader(new Ip4());
ip.source(new byte[] {2,6,0,0}); //Source Ip 2.6.0.0
ip.destination(new byte[] {1,2,3,4}); //Dest Ip 1.2.3.4
//Editing Tcp layer
Tcp tcp = packet.getHeader(new Tcp());
tcp.destination(5555); //Port destination 5555
if (pcap.sendPacket(packet) != Pcap.OK) {
System.err.println(pcap.getErr());
}
