TCP(Transmission Control protocal)

TCP is based on connection which means sending end must creat a stable connection to receiving end. This operation called three-way handshake.

UDP(User Data protocal)

Data transmission based on UDP don’t need to build connection before. The sending post send out data as soon as possible. It doesn’t make sure the receiver can receive data completely and correctly.

TCP	UDP
reliable and stable	not reliable
mass of data	small data
slow	fast
O2 byte stream	O2 message
one to one	one to many
more system resource	less system resourse
HTTP,FTP	QQ Voice QQ video

　　

UDP应用场景：

1. 面向数据报方式
2. 网络数据大多为短消息
3. 拥有大量Client
4. 对数据安全性无特殊要求
5. 网络负担非常重，但对响应速度要求高

其他区别

1. socket()的参数不同
2. UDP Server不需要调用listen和accept
3. UDP收发数据用sendto/recvfrom函数
4. TCP：地址信息在connect/accept时确定
5. UDP：在sendto/recvfrom函数中每次均 需指定地址信息
6. UDP：shutdown函数无效