At support.bioconductor.org/p/130050/#9157234 James W. MacDonald gave a function which, if modified, might be of use with useMart ? (the post was referred to as old so I'm asking a new question). Any chance of getting a similar function for useMart rather than useEnsembl ? - or won't this work ? (I get an error saying no Port - details below). Many thanks. I've tried:

library("biomaRt")
getMart <- function(biomart, dataset, host, path, archive) {
e <- simpleError("")
while(is(e, "simpleError")) {
    e <- tryCatch(useMart(biomart, dataset, host, path, archive), error = function(x) x)
}
e}

## Europe:
gene.db <- getMart(biomart = "ENSEMBL_MART_ENSEMBL", dataset = "hsapiens_gene_ensembl", host = "https://www.ensembl.org", path = "/biomart/martservice", archive = FALSE); gene.db 
## East USA:
gene.db <- getMart(biomart = "ensembl", dataset = "hsapiens_gene_ensembl", host = "https://useast.ensembl.org", path = "/biomart/martservice", archive = FALSE); gene.db

## results from East USA:
error httr2_failure
Error in req_perform():
Failed to perform HTTP request.
Caused by error in curl::curl_fetch_memory():
URL rejected: Port number was not a decimal number between 0 and 65535
---
Backtrace:

  1. global getMart(...)
  2.   base::tryCatch(...)
  3.   base (local) tryCatchList(expr, classes, parentenv, handlers)
  4.   base (local) tryCatchOne(expr, names, parentenv, handlers[[1 L]])
  5.   base (local) doTryCatch(return(expr), name, parentenv, handler)
  6.   biomaRt::useMart(biomart, dataset, host, path, archive)
  7.     biomaRt:::.useMart(...)
  8.       biomaRt:::.listMarts(...)
  9.         biomaRt:::bmRequest(...)
 10.           httr2::req_perform(request)
 11.             base::tryCatch(...)
 12.               base (local) tryCatchList(expr, classes, parentenv, handlers)
 13.                 base (local) tryCatchOne(expr, names, parentenv, handlers[[1 L]])
 14.                   value[[3 L]](cond)

sessionInfo( )
R version 4.4.1 (2024-06-14)
Platform: aarch64-apple-darwin20
Running under: macOS Sonoma 14.6.1

Matrix products: default
BLAS:   /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/lib/libRblas.0.dylib 
LAPACK: /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/lib/libRlapack.dylib;  LAPACK version 3.12.0

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

time zone: Europe/Berlin
tzcode source: internal

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods  
[7] base     

other attached packages:
[1] biomaRt_2.60.1

loaded via a namespace (and not attached):
 [1] bit_4.5.0               jsonlite_1.8.9         
 [3] dplyr_1.1.4             compiler_4.4.1         
 [5] crayon_1.5.3            filelock_1.0.3         
 [7] tidyselect_1.2.1        Biobase_2.64.0         
 [9] xml2_1.3.6              blob_1.2.4             
[11] stringr_1.5.1           Biostrings_2.72.1      
[13] IRanges_2.38.1          progress_1.2.3         
[15] png_0.1-8               fastmap_1.2.0          
[17] R6_2.5.1                XVector_0.44.0         
[19] generics_0.1.3          curl_5.2.3             
[21] httr2_1.0.4             GenomeInfoDb_1.40.1    
[23] BiocGenerics_0.50.0     tibble_3.2.1           
[25] AnnotationDbi_1.66.0    GenomeInfoDbData_1.2.12
[27] DBI_1.2.3               pillar_1.9.0           
[29] rlang_1.1.4             utf8_1.2.4             
[31] KEGGREST_1.44.1         cachem_1.1.0           
[33] stringi_1.8.4           bit64_4.5.2            
[35] RSQLite_2.3.7           memoise_2.0.1          
[37] cli_3.6.3               magrittr_2.0.3         
[39] zlibbioc_1.50.0         digest_0.6.37          
[41] dbplyr_2.5.0            rappdirs_0.3.3         
[43] hms_1.1.3               BiocFileCache_2.12.0   
[45] lifecycle_1.0.4         S4Vectors_0.42.1       
[47] prettyunits_1.2.0       vctrs_0.6.5            
[49] glue_1.7.0              stats4_4.4.1           
[51] fansi_1.0.6             httr_1.4.7             
[53] tools_4.4.1             pkgconfig_2.0.3        
[55] UCSC.utils_1.0.0