If you've got no other way of getting files from your PC to your BBC,
you can copy beeblink_tube_serial.rom to the same place you run the
server from, and run a program on the BBC to get a copy of the ROM
transferred over.
This assumes you've got a disc drive, so it just saves the ROM (max 16K) to a file for use with your usual ROM tools.
10REM>B.TUBE
20MODE1:VDU28,0,5,39,0:DEST%=&3F00
30P%=&80:[STA&FEFE:RTS:]
40DEFPROCPSEND(A%):IF(?&FEFF AND2)<>0:CALL&80:ENDPROC
50DEFPROCSEND(A%):REPEAT:UNTIL?(&FEFF AND2)<>0:CALL&80:ENDPROC
60DEFFNPRECV:IF(?&FEFF AND1)<>0:=?&FEFE:ELSE:=-1
70DEFFNRECV:REPEAT:UNTIL(?&FEFF AND1)<>0:=?&FEFE
80PRINT"WAITING FOR DEVICE"
90REPEAT:UNTIL(?&FEFF AND8)<>0
100PRINT"SYNC 1"
110PROCSEND(&80)
120N%=0:R%=300
130REPEAT
140PROCPSEND(0)
150V%=FNPRECV:IFV%>=0:IFV%=0:N%=N%+1:ELSE:N%=0
160UNTILN%=R%
170PRINT"SYNC 2"
180REPEAT
190PROCPSEND(0)
200V%=FNPRECV
210UNTILV%<>0
220IFV%<>1:PRINT"SYNC FAILED - RESTARTING":GOTO100
230PRINT"SYNC 3"
240PROCSEND(1)
250:
260PRINT"REQUEST ROM"
270PROCSEND(&02)
280PROCSEND(&00)
290PROCSEND(&01)
300:
310PRINT"AWAIT RESPONSE"
320C%=FNRECV:IFC%<>&83:PRINT"UNEXPECTED RESPONSE: &";~C%:STOP
330FORI%=0TO3:I%?&70=FNRECV:NEXT:N%=!&70:PRINT"RECEIVING ";N%" BYTES"
340N%!DEST%=-1
350O%=-(N%-1)
360FORI%=0TON%-1
370IF((-(N%-1-I%))AND255)=0:X%=FNRECV
380I%?DEST%=FNRECV
390NEXT
400O$="SAVE R.TS "+STR$~DEST%+"+"+STR$~N%+" 0 0"
410PRINTO$
420OSCLIO$