class QHostInfo

The QHostInfo class provides static functions for host name lookups. More…

Synopsis

Methods

Static functions

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

Detailed Description

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

QHostInfo finds the IP address(es) associated with a host name, or the host name associated with an IP address. The class provides two static convenience functions: one that works asynchronously and emits a signal once the host is found, and one that blocks and returns a QHostInfo object.

To look up a host’s IP addresses asynchronously, call lookupHost() , which takes the host name or IP address, a receiver object, and a slot signature as arguments and returns an ID. You can abort the lookup by calling abortHostLookup() with the lookup ID.

Example:

# To find the IP address of qt-project.org
QHostInfo::lookupHost("qt-project.org", self.printResults)
# To find the host name for 4.2.2.1
QHostInfo::lookupHost("4.2.2.1", self.printResults)

The slot is invoked when the results are ready. The results are stored in a QHostInfo object. Call addresses() to get the list of IP addresses for the host, and hostName() to get the host name that was looked up.

If the lookup failed, error() returns the type of error that occurred. errorString() gives a human-readable description of the lookup error.

If you want a blocking lookup, use the fromName() function:

info = QHostInfo.fromName("qt-project.org")

QHostInfo supports Internationalized Domain Names (IDNs) through the IDNA and Punycode standards.

To retrieve the name of the local host, use the static localHostName() function.

QHostInfo uses the mechanisms provided by the operating system to perform the lookup. As per RFC 6724 there is no guarantee that all IP addresses registered for a domain or host will be returned.

Note

Since Qt 4.6.1 QHostInfo is using multiple threads for DNS lookup instead of one dedicated DNS thread. This improves performance, but also changes the order of signal emissions when using lookupHost() compared to previous versions of Qt.

Note

Since Qt 4.6.3 QHostInfo is using a small internal 60 second DNS cache for performance improvements.

See also

QAbstractSocket RFC 3492RFC 6724

class HostInfoError

This enum describes the various errors that can occur when trying to resolve a host name.

Constant

Description

QHostInfo.NoError

The lookup was successful.

QHostInfo.HostNotFound

No IP addresses were found for the host.

QHostInfo.UnknownError

An unknown error occurred.

See also

error() setError()

__init__(d)
Parameters:

d – QHostInfo

Constructs a copy of other.

__init__([lookupId=-1])
Parameters:

lookupId – int

Constructs an empty host info object with lookup ID id.

See also

lookupId()

static abortHostLookup(lookupId)
Parameters:

lookupId – int

Aborts the host lookup with the ID id, as returned by lookupHost() .

addresses()
Return type:

.list of QHostAddress

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

Returns the list of IP addresses associated with hostName() . This list may be empty.

Example:

info = QHostInfo()
...
if not info.addresses().isEmpty():
    address = info.addresses().first()
    # use the first IP address

See also

setAddresses() hostName() error()

error()
Return type:

HostInfoError

Returns the type of error that occurred if the host name lookup failed; otherwise returns NoError .

errorString()
Return type:

str

If the lookup failed, this function returns a human readable description of the error; otherwise “Unknown error” is returned.

static fromName(name)
Parameters:

name – str

Return type:

QHostInfo

Looks up the IP address(es) for the given host name. The function blocks during the lookup which means that execution of the program is suspended until the results of the lookup are ready. Returns the result of the lookup in a QHostInfo object.

If you pass a literal IP address to name instead of a host name, QHostInfo will search for the domain name for the IP (i.e., QHostInfo will perform a reverse lookup). On success, the returned QHostInfo will contain both the resolved domain name and IP addresses for the host name.

See also

lookupHost()

hostName()
Return type:

str

Returns the name of the host whose IP addresses were looked up.

static localDomainName()
Return type:

str

Returns the DNS domain of this machine.

Note

DNS domains are not related to domain names found in Windows networks.

See also

hostName()

static localHostName()
Return type:

str

Returns this machine’s host name, if one is configured. Note that hostnames are not guaranteed to be globally unique, especially if they were configured automatically.

This function does not guarantee the returned host name is a Fully Qualified Domain Name (FQDN). For that, use fromName() to resolve the returned name to an FQDN.

This function returns the same as QSysInfo::machineHostName().

lookupHost(arg__1, arg__2)
Parameters:

  • arg__1 – str

  • arg__2 – PyCallable

static lookupHost(name, receiver, member)
Parameters:

  • name – str

  • receiver – QObject

  • member – str

Return type:

int

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

Looks up the IP address(es) associated with host name name, and returns an ID for the lookup. When the result of the lookup is ready, the slot or signal member in receiver is called with a QHostInfo argument. The QHostInfo object can then be inspected to get the results of the lookup.

The lookup is performed by a single function call, for example:

QHostInfo::lookupHost("www.kde.org", self.lookedUp)

The implementation of the slot prints basic information about the addresses returned by the lookup, or reports an error if it failed:

def lookedUp(self, host):

    if host.error() != QHostInfo.NoError:
        print("Lookup failed:", host.errorString())
        return

    addresses = host.addresses()
    for address in addresses:
        print("Found address:", address.toString())

If you pass a literal IP address to name instead of a host name, QHostInfo will search for the domain name for the IP (i.e., QHostInfo will perform a reverse lookup). On success, the resulting QHostInfo will contain both the resolved domain name and IP addresses for the host name. Example:

QHostInfo::lookupHost("4.2.2.1", self.lookedUp)

Note

There is no guarantee on the order the signals will be emitted if you start multiple requests with lookupHost().

Note

In Qt versions prior to 6.7, this function took receiver as (non-const) QObject*.

See also

abortHostLookup() addresses() error() fromName()

lookupId()
Return type:

int

Returns the ID of this lookup.

setAddresses(addresses)
Parameters:

addresses – .list of QHostAddress

Sets the list of addresses in this QHostInfo to addresses.

See also

addresses()

setError(error)
Parameters:

error – HostInfoError

Sets the error type of this QHostInfo to error.

setErrorString(errorString)
Parameters:

errorString – str

Sets the human readable description of the error that occurred to str if the lookup failed.

setHostName(name)
Parameters:

name – str

Sets the host name of this QHostInfo to hostName.

See also

hostName()

setLookupId(id)
Parameters:

id – int

Sets the ID of this lookup to id.

swap(other)
Parameters:

other – QHostInfo

Swaps host-info other with this host-info. This operation is very fast and never fails.