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cserviceportgetaddrinfo

service to port number like getaddrinfo

In C you can use a service name to get the port number when using getaddrinfo, like this:

getaddrinfo("stackoverflow.com", "http", &hints, &results);

This will assign 80 (big endian) to the first two bytes (uint16_t) of results->ai_addr.

Is there some easy way to get the port number from ?only? giving the service name? I need this for the server side, where I want to allow the user to specify either port number or service name for the port to bind and listen to.

Solution

  • Using getaddrinfo with a null pointer for the hostname and AI_PASSIVE in the flags will give you a sockaddr you can bind on for running a server. See the documentation for getaddrinfo:

    http://pubs.opengroup.org/onlinepubs/9699919799/functions/getaddrinfo.html