R会话能否同时建立文本与二进制Socket连接？跨机异常及方案

我正在编写R程序，需要在两台机器间维持一个用于文本通信的Socket连接，同时建立第二个Socket传输文件，但跨机器运行时方案失效。

测试代码 #

test-server.R #

textSocket <- socketConnection(host="192.168.56.101", port=9998, blocking=TRUE, server=TRUE, encoding="utf-8", timeout=300, open="r+")

fileSize <- as.integer(readLines(textSocket, 1))

binSocket <- socketConnection(host="192.168.56.101", port=9999, blocking=TRUE, server=TRUE, timeout=15, open="rb")
fileData <- readBin(binSocket, "raw", n=fileSize)
close(binSocket)

outFile <- file("fromClient.txt", open="wb")
writeBin(fileData, outFile)
close(outFile)

close(textSocket)

test-client.R #

textSocket <- socketConnection(host="192.168.56.101", port=9998, server=FALSE, blocking=TRUE, encoding="utf-8", timeout=86400, open="r+")

fileSize <- as.integer(file.info("toServer.txt")$size)
writeLines(toString(fileSize), textSocket)

inFile <- file("toServer.txt", open="rb")
fileData <- readBin(inFile, "raw", n=fileSize)
close(inFile)

binSocket <- socketConnection(host="192.168.56.101", port=9999, blocking=TRUE, server=FALSE, timeout=300, open="rb")
writeBin(fileData, binSocket)
close(binSocket)

close(textSocket)

运行结果 #

• 本地同机器测试：将所有文件（含toServer.txt）放在IP为192.168.56.101的机器上，两个独立R会话用source()运行程序，一切正常，工作目录生成符合预期的fromClient.txt，无警告或错误。
• 跨机器测试：在IP为192.168.56.102的机器上运行test-client.R，程序执行到创建binSocket步骤后报错：

客户端错误 #

Error in socketConnection(host = "192.168.56.101", port = 9999, blocking = TRUE,  :
  cannot open the connection
In addition: Warning message:
In socketConnection(host = "192.168.56.101", port = 9999, blocking = TRUE,  :
  192.168.56.101:9999 cannot be opened

服务器端错误 #

Error in socketConnection(host = "192.168.56.101", port = 9999, blocking = TRUE,  :
  cannot open the connection
In addition: Warning message:
In socketConnection(host = "192.168.56.101", port = 9999, blocking = TRUE,  :
  problem in listening on this socket

环境背景 #

• 两台均为VirtualBox“仅主机网络”设置的Ubuntu 22虚拟机，已安装R和RStudio
• 端口9998、9999无进程占用，更换端口后问题仍存在

疑问 #

R是否不允许单个会话创建两个同时存在的Socket？我在文档和相关线程中未找到相关说明，不过确实很少有人用基础R进行Socket开发。

更新：替代方案 #

无需使用双Socket即可同时传输文本和文件！若将主Socket（代码中的textSocket）以参数open="r+b"打开，即可在同一个Socket上同时使用readLines()、writeLines()、readBin()和writeBin()，只需跟踪数据大小即可。

内容的提问来源于stack exchange，提问作者Hilfigertout