You can find protobuf 2.5.0 on this page: github

pi@node5:~ $ wget

pi@node5:~ $ tar -xzvf protobuf-2.5.0.tar.gz 


install automake autoconf

pi@node5:~ $ sudo apt-get install automake autoconf libtool
pi@node5:~ $ cd protobuf-2.5.0
pi@node5:~ $ ./
pi@node5:~ $ ./configure --prefix=/usr
pi@node5:~ $ make
pi@node5:~ $ sudo make install
pi@node5:~ $ sudo ldconfig
pi@node5:~ $ protoc --version


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