UUCP `t' Protocol
The `t' protocol is intended for use on links which provide reliable end-to-end connections, such as TCP. It does no error checking or flow control, and requires an eight bit clear channel.
I believe the `t' protocol originated in BSD versions of UUCP.
When a UUCP package transmits a command, it first gets the length of the command string, C. It then sends `((C / 512) + 1) * 512' bytes (the smallest multiple of 512 which can hold C bytes plus a null byte) consisting of the command string itself followed by trailing null bytes.
When a UUCP package sends a file, it sends it in blocks. Each block contains at most 1024 bytes of data. Each block consists of four bytes containing the amount of data in binary (most significant byte first, the same format as used by the Unix function `htonl') followed by that amount of data. The end of the file is signalled by a block containing zero bytes of data.