6. Addresses

The low-level format of the addresses are different depending on the mode of communication you have chosen. A function is provided by each of the lower layers to map a user-friendly string-form address to the binary form required by the lower layers.

    void *cs_straddr(COMSTACK handle, const char *str);

The format for TCP/IP and SSL addresses is:

    <host> [ ':' <portnum> ]

The hostname can be either a domain name or an IP address. The port number, if omitted, defaults to 210.

For TCP/IP and SSL, the special hostnames @, maps to IN6ADDR_ANY_INIT with IPV4 binding as well (bindv6only=0), The special hostname @4 binds to INADDR_ANY (IPV4 only listener). The special hostname @6 binds to IN6ADDR_ANY_INIT with bindv6only=1 (IPV6 only listener).

For UNIX sockets, the format of an address is the socket filename.

When a connection has been established, you can use

    const char *cs_addrstr(COMSTACK h);

to retrieve the host name of the peer system. The function returns a pointer to a static area, which is overwritten on the next call to the function.

A fairly recent addition to the COMSTACK module is the utility function

    COMSTACK cs_create_host (const char *str, int blocking, void **vp);

which is just a wrapper for cs_create and cs_straddr. The str is similar to that described for cs_straddr but with a prefix denoting the COMSTACK type. Prefixes supported are tcp: and unix: and ssl: for TCP/IP and UNIX and SSL respectively. If no prefix is given, then TCP/IP is used. The blocking is passed to function cs_create. The third parameter vp is a pointer to COMSTACK stack type specific values. Parameter vp is reserved for future use. Set it to NULL.