这个错误的原因是在Python 3中，字符串是Unicode，但是在网络上传输时，数据需要是字节.所以...一些建议:

The reason for this error is that in Python 3, strings are Unicode, but when transmitting on the network, the data needs to be bytes instead. So... a couple of suggestions:

1. 建议使用 c.sendall() 而不是 c.send() 以防止可能出现的问题，即您可能没有通过一次调用发送整个 msg(请参阅 docs).
2. 对于文字，为字节字符串添加 'b':c.sendall(b'Thank you for connection')
3. 对于变量，您需要将 Unicode 字符串编码为字节字符串(见下文)

1. Suggest using c.sendall() instead of c.send() to prevent possible issues where you may not have sent the entire msg with one call (see docs).
2. For literals, add a 'b' for bytes string: c.sendall(b'Thank you for connecting')
3. For variables, you need to encode Unicode strings to byte strings (see below)

***解决方案(应同时使用 2.x 和 3.x):

Best solution (should work w/both 2.x & 3.x):

output = 'Thank you for connecting'
c.sendall(output.encode('utf-8'))

结语/背景:这在 Python 2 中不是问题，因为字符串已经是字节字符串——您的 OP 代码可以在该环境中完美运行.Unicode 字符串在 1.6 & 版本中被添加到 Python 中.2.0 但在 3.0 成为默认字符串类型之前退居二线.另请参阅 this similar question 以及 this one.

Epilogue/background: this isn't an issue in Python 2 because strings are bytes strings already -- your OP code would work perfectly in that environment. Unicode strings were added to Python in releases 1.6 & 2.0 but took a back seat until 3.0 when they became the default string type. Also see this similar question as well as this one.