Bind and socket programming

Question

Is it necessary to bind a socketfd to a IP addrees while writting a server socket programming. I mean is it possble to write a socket programming without calling bind system call? Like socket -> listen -> accept -> read/write/ -> close.

Answer 1

socket should be bind to port or unix socket file. Do you mean you don't want to define port number for listen ? Then bind port number 0. It works with random port.

memset((char *) &reader_addr, 0, sizeof(reader_addr));
reader_addr.sin_family = PF_INET;
reader_addr.sin_addr.s_addr = htonl(INADDR_ANY);
reader_addr.sin_port = 0;

if (bind(server_fd, (struct sockaddr *)&reader_addr, sizeof(reader_addr)) < 0) {
    perror("reader: bind");
    exit(1);
}

Answer 2

You use bind at the server end.

Simply imagine it is a switch board for your office. The bind gives it a phone number so that other people know what number to phone. The the operator listen answers and puts the call through (ie process it).