Simplifying socket connect, allow for using host address

[gilbertlee-amd]

Motivation

Attempting to make using socket connections simpler.
The new flow is now:

First rank just needs to specify the number of ranks in total using TB_NUM_RANKS

Node 0> TB_NUM_RANKS=4 ./TransferBench

This will then provide connection information for other ranks:

[INFO] TB_MASTER_ADDR not set; using detected IPv4 12.34.56.78
[INFO] Socket rank 0: on each other host set TB_RANK to a unique value in 1..3, then for example:
       TB_NUM_RANKS=4 TB_MASTER_ADDR=12.34.56.78 TB_MASTER_PORT=29500 TB_RANK=1
[INFO] Waiting for connections from 3 other rank(s) [TB_MASTER_ADDR=12.34.56.78 TB_MASTER_PORT=29500]

Other ranks can then connect by providing those enviroment variables (and adjusting TB_RANK for each node)

Node 1> TB_NUM_RANKS=4 TB_MASTER_ADDR=12.34.56.78 TB_MASTER_PORT=29500 TB_RANK=1 ./TransferBench
Node 2> TB_NUM_RANKS=4 TB_MASTER_ADDR=12.34.56.78 TB_MASTER_PORT=29500 TB_RANK=2 ./TransferBench
Node 3> TB_NUM_RANKS=4 TB_MASTER_ADDR=12.34.56.78 TB_MASTER_PORT=29500 TB_RANK=3 ./TransferBench

Host address can also be used for setting TB_MASTER_ADDR

Node 0> TB_NUM_RANKS=4 TB_MASTER_ADDR=hostname ./TransferBench

Technical Details

Minor changes to the socket code

[Copilot]

Pull request overview

This PR streamlines TransferBench’s socket-based multi-rank startup so rank 0 can start listening with only TB_NUM_RANKS set, auto-detect (or resolve) a reachable master address, and print concrete connection instructions for worker ranks.

Changes:

• Update socket communicator enablement to trigger when TB_NUM_RANKS>=2, default TB_RANK to 0, and require TB_MASTER_ADDR only for workers.
• Add IPv4 auto-detection for rank 0 (TB_MASTER_IFACE optional) and allow hostname resolution for TB_MASTER_ADDR via getaddrinfo.
• Refresh env var help/usage text and changelog to reflect the simplified socket flow.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/header/TransferBench.hpp	Implements new socket setup flow, IPv4 detection, and hostname-to-IPv4 resolution.
src/client/EnvVars.hpp	Updates printed documentation for socket-related environment variables (incl. TB_MASTER_IFACE).
src/client/Client.cpp	Updates CLI usage examples to match the new socket startup flow.
CHANGELOG.md	Notes the socket communicator usability change for the release notes.

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