A port is nothing more than an integer that uniquely identifies an endpoint of a communication stream. Only one process per machine can listen on the same port number.
A port is a maritime facility which may comprise one or more wharves where ships may dock to load and discharge passengers and cargo. Although usually situated on a sea coast or estuary, some ports, such as Hamburg, Manchester and Duluth, are many miles inland, with access to the sea via river or canal. Because of their roles as a port of entry for immigrants many port cities such as London, New York, Shanghai, Los Angeles, Singapore and Vancouver have experienced dramatic multi-ethnic and multicultural changes.
Ports are extremely important to the global economy, responsible for 70% of global merchandise trade by value. For this reason, ports are often high-concentrations of the global population—providing the labor for processing and handling the goods and related services for the ports. Today, by far the greatest growth in port development is in Asia, the continent with some of the world's largest and busiest ports, such as Singapore and the Chinese ports of Shanghai and Ningbo-Zhoushan. As of 2020, the busiest passenger port in the world is the Port of Helsinki in Finland. However, ports can also be very small and only serve local fishing or tourism.
Ports are responsible for a number of environmental impacts on local ecologies and water ways, for example direct effects on water quality, caused by dredging, spills and other pollution. Ports are heavily effected by the changing environmental factors caused by climate change. Importantly most port infrastructure is extremely vulnerable to sea level rise, due to its low-lying nature, making it vulnerable extreme weather and coastal flooding. Internationally, global ports are beginning to identify ways to improve coastal management practices and integrate climate change adaptation practices into their construction.
