Let's say HPEL or SystemOut log has something like this.

[3/2/23 20:17:55:619 CST] 00000078 ThreadPool    I   WSVR0652W: The size of thread pool "WebContainer" has reached 80 percent of its maximum.
[3/2/23 20:18:02:690 CST] 00000078 ThreadPool    I   WSVR0652W: The size of thread pool "WebContainer" has reached 100 percent of its maximum.
[3/2/23 20:18:38:827 CST] 00000078 TCPChannel    W   TCPC0004W: TCP Channel TCP_2 has exceeded the maximum number of open connections 100.

In this example, TCP_2 should be found in the /opt/WebSphere/AppServer/profiles/your_profile/config/cells/your_cell/nodes/your_node/servers/your_server/server.xml file. Notice the maxOpenConnections is set to 100.

<transportChannels xmi:type="channelservice.channels:TCPInboundChannel" xmi:id="TCPInboundChannel_2" name="TCP_2" endPointName="WC_defaulthost" maxOpenConnections="100" inactivityTimeout="60" threadPool="ThreadPool_WC"/>

Notice the TCP channel is using the WC_defaulthost end point. This can be seen in the WebSphere admin console at Servers > Server Types > WebSphere application servers > your application server > Ports.

One or more applications running in the WebSphere application server may have some issue where connections to a remote system are being opened and not being closed.