Socket Types

Socket types define the communication properties visible to the application. Processes communicate only between sockets of the same type. There are five types of socket.

• A stream socket provides two-way, sequenced, reliable, and unduplicated flow of data with no record boundaries. A stream operates much like a telephone conversation. The socket type is SOCK_STREAM, which, in the Internet domain, uses Transmission Control Protocol (TCP).

• A datagram socket supports a two-way flow of messages. A on a datagram socket may receive messages in a different order from the sequence in which the messages were sent. Record boundaries in the data are preserved. Datagram sockets operate much like passing letters back and forth in the mail. The socket type is SOCK_DGRAM, which, in the Internet domain, uses User Datagram Protocol (UDP).

• A sequential packet socket provides a two-way, sequenced, reliable, connection, for datagrams of a fixed maximum length. The socket type is SOCK_SEQPACKET. No protocol for this type has been implemented for any protocol family.

• A raw socket provides access to the underlying communication protocols. These sockets are usually datagram oriented, but their exact characteristics depend on the interface provided by the protocol.