Can TCP protocol be considered blocking in the context of synchronous data transfer?

Yes, the TCP protocol can be considered blocking in the context of synchronous data transfer if standard blocking I/O is used. This means that when calling read or write operations, the execution thread is suspended until the operation completes (for example, until data is received or sent).

However, the TCP protocol itself does not impose strict restrictions on blocking or non-blocking behavior — it depends on the implementation at the operating system level and the APIs used. For example, in Java, non-blocking channels (NIO) can be used, which allow working with TCP without blocking.

In summary:

• With standard synchronous TCP connection usage, I/O operations block the thread.
• For non-blocking behavior, special mechanisms and APIs are required.