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I'm trying download file via TFTP on Ubuntu 16.04LTS machine from TFTP server (TFTPD32) running on Windows 7 machine. On Ubuntu every time I got error Transfer timed out. On Windows 7 PC Windows firewall is configured to allow tftp traffic, but I also tried with firewall completely disabled, and Anti-virus software disabled - same result. Different internet connection (different ISP) on Ubuntu and Windows computer. Below is tftp output on Ubuntu:

tftp> get test.bin
getting from 63.231.242.57:test.bin to test.bin [octet]
Transfer timed out.

and Tftpd32 log on Windows PC:

Connection received from 213.173.91.204 on port 48859 [12/10 23:45:17.697]
Read request for file <test.bin>. Mode octet [12/10 23:45:17.697]
Using local port 62693 [12/10 23:45:17.697]
WARNING : Last block #1 not acked for file <test.bin> [12/10 23:45:47.228]
<test.bin>: sent 0 blk, 0 bytes in 48 s. 6 blks resent [12/10 23:45:47.228]
WARNING : Last block #1 not acked for file <test.bin> [12/10 23:45:50.832]
<test.bin>: sent 0 blk, 0 bytes in 48 s. 6 blks resent [12/10 23:45:50.832]
WARNING : Last block #1 not acked for file <test.bin> [12/10 23:45:55.777]
<test.bin>: sent 0 blk, 0 bytes in 48 s. 6 blks resent [12/10 23:45:55.777]
WARNING : Last block #1 not acked for file <test.bin> [12/10 23:46:00.862]
<test.bin>: sent 0 blk, 0 bytes in 48 s. 6 blks resent [12/10 23:46:00.862]

As far I know, TFTP requires every data block to be ACKed before the next block can be sent.

http://tools.ietf.org/html/rfc1350

  1. Overview of the Protocol .... length blocks of 512 bytes. Each data packet contains one block of data, and must be acknowledged by an acknowledgment packet before the next packet can be sent.

tftpd32 server sends data to the tftp client in chunks. The file size is 265 bytes, then there is only one block. So TFTP server don't responds with an ACK acknowledgement of the requested block size.

How to solve this issue?

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