In previous versions of the IG publisher, I was able to get it to work behind a network proxy by using the following command (note: actual proxy server changed in this example):

java -Xms4g -Xmx8g -Dhttp.proxyHost=my.proxy.org -Dhttp.proxyPort=80 -Dhttps.proxyHost=my.proxy.org -Dhttps.proxyPort=80 -jar org.hl7.fhir.igpublisher.jar -ig ig.json

Somewhere between R3 and R4, however, something appears to have changed in the IG Publisher and the above no longer works. I also tried using a -proxy flag, as suggested on Zulip, but that does not work either. When I run it, it seems to go wrong around connecting to the terminology server:

Connect to Terminology Server at [http://tx.fhir.org |] (08.0340sec)
-tx cache miss: Connect to http://tx.fhir.org//r2
Publishing Content Failed: Error sending Http Request (00:02:39.0083sec)
(00:02:39.0083sec)
Use -? to get command line help (00:02:39.0083sec)
(00:02:39.0084sec)
Stack Dump (for debugging): (00:02:39.0084sec)
org.hl7.fhir.dstu2.utils.client.EFhirClientException: Error sending Http Request
at org.hl7.fhir.dstu2.utils.client.ClientUtils.sendRequest(ClientUtils.java:250)
at org.hl7.fhir.dstu2.utils.client.ClientUtils.issueResourceRequest(ClientUtils.java:175)
at org.hl7.fhir.dstu2.utils.client.ClientUtils.issueResourceRequest(ClientUtils.java:159)
at org.hl7.fhir.dstu2.utils.client.ClientUtils.issueResourceRequest(ClientUtils.java:150)
at org.hl7.fhir.dstu2.utils.client.ClientUtils.issueGetResourceRequest(ClientUtils.java:97)
at org.hl7.fhir.dstu2.utils.client.FHIRToolingClient.getConformanceStatementQuick(FHIRToolingClient.java:164)
at org.hl7.fhir.dstu2.utils.client.FHIRToolingClient.getConformanceStatementQuick(FHIRToolingClient.java:155)
at org.hl7.fhir.convertors.TerminologyClientR2.getCapabilitiesStatementQuick(TerminologyClientR2.java:69)
at org.hl7.fhir.r4.context.SimpleWorkerContext.connectToTSServer(SimpleWorkerContext.java:218)
at org.hl7.fhir.igtools.publisher.Publisher.initializeFromJson(Publisher.java:1113)
at org.hl7.fhir.igtools.publisher.Publisher.initialize(Publisher.java:944)
at org.hl7.fhir.igtools.publisher.Publisher.execute(Publisher.java:523)
at org.hl7.fhir.igtools.publisher.Publisher.main(Publisher.java:4925)
Caused by: org.apache.http.conn.HttpHostConnectException: Connection to http://tx.fhir.org refused
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:190)
at org.apache.http.impl.conn.ManagedClientConnectionImpl.open(ManagedClientConnectionImpl.java:294)
at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:645)
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:480)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:906)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:805)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:784)
at org.hl7.fhir.dstu2.utils.client.ClientUtils.sendRequest(ClientUtils.java:248)
... 12 more
Caused by: java.net.ConnectException: Operation timed out (Connection timed out)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:127)
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180)
... 19 more

See: https://chat.fhir.org/#narrow/stream/99-IG-creation/subject/IG.20Publisher.20Proxy.20Issue.3F