In April 1971, American ping-pong player Glenn Cowan boarded the wrong bus during the world championships in Nagoya, Japan. He missed the US team's bus and got on the next one, only to find himself on the Chinese team's bus.

At that time, US-China relations had been hostile for decades. On board the bus, Chinese player Zhuang Zedong saw the unfamiliar American, stepped forward and introduced himself.

"They didn't speak each other's languages, but somehow they were able to communicate because they tried. And their picture was taken and traveled around the world. They started a dialogue between America and China that continues today," film producer Bill Einreinhofer told China Daily.

Einreinhofer, a three-time Emmy Award-winning producer, documented the period of history in his new film Your Serve or Mine. The encounter led to what became known as Ping-Pong Diplomacy.

The group of nine US table tennis players embarked on a milestone journey to China, helping break the ice between Beijing and Washington and laying the groundwork for the eventual establishment of diplomatic relations.

Ping-Pong Diplomacy "was the starting point for a back-channel way that two countries with profound differences could find some way to communicate, some way to talk outside of the glare of the media," Einreinhofer said.

The documentary is now streaming on the Public Broadcasting Service (PBS) in the US. The New York Film Academy (NYFA) hosted a premiere for the film on Wednesday.

"The underlying message of the film is that, in fact, even if we are coming from very different cultures and very different places, there are some similarities," Einreinhofer said.