File zip
https://files.cnblogs.com/files/dong1/cs556-3rd-tutorial.zip
Copyright
https://www.csd.uoc.gr/~hy556/material/tutorials/cs556-3rd-tutorial.pdf
Sample C socket programs
https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.1.0/com.ibm.zos.v2r1.hala001/samples.htm