oschina.net 是目前领先的中文开源技术社区。我们传播开源的理念，推广开源项目，为 it 开发者提供了一个发现、使用、并交流开源技术的平台

wireshark: the world's most popular network protocol analyzer

winscp is a free file manager for windows supporting ftp, sftp, s3 and webdav.

stack overflow is the largest, most trusted online community for developers to learn, share​ ​their programming ​knowledge, and build their careers.

github is where over 100 million developers shape the future of software, together. contribute to the open source community, manage your git repositories, review code like a pro, track bugs and features, power your ci/cd and devops workflows, and secure code before you commit it.

q&a for ubuntu users and developers

the main openssh page

sourceforge provides free & fast open source software downloads and development, and business software reviews and comparisons featuring the largest open source and business software directory.