The Grid Community Toolkit documentation was taken from the Globus Toolkit 6.0 documentation. As a result, there may be inaccuracies and outdated information. Please report any problems to the Grid Community Forums as GitHub issues.

GCTXIO → GT 6.0 Release Notes: XIO

Component Overview

Globus XIO is an extensible input/output library written in C for the Grid Community Toolkit. It provides a single API (open/close/read/write) that supports multiple wire protocols, with protocol implementations encapsulated as drivers. The XIO drivers distributed with 6.0 include TCP, UDP, file, HTTP, GSI, GSSAPI_FTP, TELNET and queuing. In addition, Globus XIO provides a driver development interface for use by protocol developers. This interface allows the developer to concentrate on writing protocol code rather than infrastructure, as XIO provides a framework for error handling, asynchronous message delivery, timeouts, etc. The XIO driver-based approach maximizes the reuse of code by supporting the notion of a driver stack. XIO drivers can be written as atomic units and stacked on top of one another. This modularization provides maximum flexibility and simplifies the design and evaluation of individual protocols.

Feature summary

Supported Features

  • Driver specific string attributes. Set values like tcp buffer size via string at runtime.

  • UDT driver.

  • Mode E Driver

  • Telnet Driver

  • Queuing Driver

  • Ordering Driver

  • Dynamically loadable drivers.

  • Single API to swappable IO implementations.

  • Asynchronous IO support.

  • Native timeout support.

  • Data descriptors for providing driver specific hints.

  • Modular driver stacks to maximize code reuse.

  • TCP, UDP, file, HTTP, telnet, mode E, GSI drivers.

Deprecated Features

  • GSSAPI_FTP driver now distributed with the GridFTP Server

Summary of Changes in XIO

New Features: XIO

  • None

Improvements: XIO


Fixed Bugs for XIO

  • GT-546: HTTP transfers larger than 4GB fail

Known Problems in XIO

  • GT-54: Globus XIO close call can deadlock

Technology dependencies

XIO depends on the following GCT components:

  • Globus Core

  • Globus Common

  • Globus GSSAPI

Tested platforms

Tested Platforms for XIO:

Table 1. Tested Platforms
Operating System Distribution Version(s) Architecture(s)



5, 6

i386, x86_64




20, 21, 22

i386, x86_64

Red Hat Enterprise Linux

5, 6

i386, x86_64



Scientific Linux

5, 6

i386, x86_64



SUSE Linux Enterprise Server




6, 7, 8

i386, amd64


12.04LTS, 14.04LTS, 14.10, 15.04

i386, amd64

Mac OS X


i386, x86_64





Windows 7


i386, x86_64


i386, x86_64

Backward compatibility summary

Protocol changes since GT version 5.2

  • None.

API changes since GT version 5.2

  • globus_xio_stack_copy added to the API. This allows a user to duplicated a configured stack.

  • globus_xio_driver_set_eof_received added to the driver API. This function allows drivers to have multiple outstanding reads at one time.

  • globus_xio_driver_eof_received added to the driver API. Working in conjunction with globus_xio_driver_set_eof_received to allow drivers to have multiple outstanding reads.

  • Users can now pass in a NULL callback for timeouts and it is assumed that when time expires the user wants the operation to timeout. Previously a user callback was required where the user would decide if they wanted the timeout.

Associated Standards

Adoption of standards in XIO is determined by the drivers. All drivers distributed by XIO are compliant with the protocol they implement.

For More Information

See XIO for more information about this component.