The
Port Mapper Daemon (PMD) is a network service that operates on the
Internet Protocol (IP) network layer. Its main purpose is to facilitate communication between networked devices by mapping network port numbers to specific services or processes running on those devices. The PMD is typically used in conjunction with the
Remote Procedure Call (RPC) mechanism to enable clients to locate and communicate with specific services on remote servers.
Here's a breakdown of the key aspects of the Port Mapper Daemon :
* Port Mapping : The PMD maintains a mapping of network port numbers to specific services or processes on a device. When a client wants to access a particular service on a server, it can query the PMD to obtain the port number associated with that service. The client can then use the obtained port number to establish a connection and communicate with the desired service.
* Protocol Independence : The PMD is independent of the transport protocol being used. It can handle port mappings for various protocols, such as TCP (Transmission Control Protocol) or UDP (User Datagram Protocol). The protocol used for communication with the PMD depends on the specific implementation and configuration.
* Service Location : Clients can query the PMD to locate services on remote servers. By requesting the mapping of a specific service name or identifier, the client can obtain the corresponding port number associated with that service. This enables clients to dynamically discover and connect to services without prior knowledge of the exact port numbers they are listening on.
* Dynamic Port Allocation : In some cases, the PMD can allocate ports dynamically to services. This allows services to be assigned available port numbers on-demand, without conflicting with other services. Dynamic port allocation can help manage port usage efficiently, especially in scenarios where multiple services need to coexist on the same device or server.
* Standardization : The Port Mapper Daemon is part of the Network File System (NFS) standard, which specifies a distributed file system protocol commonly used in Unix-like operating systems. The PMD is defined in the NFS specification as an integral component for locating and accessing NFS services on remote servers.
