I am trying to use Indy10 ReadBytes() in Delphi 2007 to read a large download of a series of data segments formatted as [#bytes]\r\n where #bytes indicates the number of bytes. My algorithm is:
- Use ReadBytes() to get the [#]\r\n text, which is normally 10 bytes.
- Use ReadBytes() to get the specified # data bytes.
- Go to step 1 if more data segments need to be processed, i.e., # is negative.
This works well but frequently I don't get the expected text at step 1. Here's a short example after 330 successful data segments:
Data received from last step 2 ReadBytes(). NOTE embedded Step 1 [-08019]\r\n text.
Line|A033164|B033164|C033164|D033164|E033164|F033164|G033164|H033164|EndL\r|Begin
Line|A033165|B033165|C033165|D033165|E033165|F033165|G033165|H033165|EndL\r|Begin
Line|A033166|B033166|C033166|D033166|E033166|F033166|G033166|H033166|EndL\r[-08019]
\r\n|Begin
Line|A033167|B033167|C033167|D033167|E033167|F033167|G033167|H033167|EndL\r|Begin
Line|A033168|B033168|C033168|D033168|E033168|F033168|G033168|H033168|EndL\r|Begin
Socket data captured by WireShark.
0090 30 33 33 31 36 36 7c 42 30 33 33 31 36 36 7c 43 033166|B033166|C
00a0 30 33 33 31 36 36 7c 44 30 33 33 31 36 36 7c 45 033166|D033166|E
00b0 30 33 33 31 36 36 7c 46 30 33 33 31 36 36 7c 47 033166|F033166|G
00c0 30 33 33 31 36 36 7c 48 30 33 33 31 36 36 7c 45 033166|H033166|E
00d0 6e 64 4c 0d ndL.
No. Time Source Destination Protocol Length Info
2837 4.386336000 000.00.247.121 000.00.172.17 TCP 1514 40887 > 57006 [ACK] Seq=2689776 Ack=93 Win=1460 Len=1460
Frame 2837: 1514 bytes on wire (12112 bits), 1514 bytes captured (12112 bits) on interface 0
Ethernet II, Src: Cisco_60:4d:bf (e4:d3:f1:60:4d:bf), Dst: Dell_2a:78:29 (f0:4d:a2:2a:78:29)
Internet Protocol Version 4, Src: 000.00.247.121 (000.00.247.121), Dst: 000.00.172.17 (000.00.172.17)
Transmission Control Protocol, Src Port: 40887 (40887), Dst Port: 57006 (57006), Seq: 2689776, Ack: 93, Len: 1460
Data (1460 bytes)
0000 5b 2d 30 38 30 31 39 5d 0d 0a 7c 42 65 67 69 6e [-08019]..|Begin
0010 20 4c 69 6e 65 7c 41 30 33 33 31 36 37 7c 42 30 Line|A033167|B0
0020 33 33 31 36 37 7c 43 30 33 33 31 36 37 7c 44 30 33167|C033167|D0
0030 33 33 31 36 37 7c 45 30 33 33 31 36 37 7c 46 30 33167|E033167|F0
Does anyone know why this happens? Thanks
More information. We do socket reading from a single thread and don't call Connected() while reading. Here's relevant code snippet:
AClientDebugSocketContext.Connection.Socket.ReadBytes(inBuffer,byteCount,True);
numBytes := Length(inBuffer);
Logger.WriteToLogFile(BytesToString: '+BytesToString(inBuffer,0,numBytes),0);
Move(inBuffer[0], Pointer(Integer(Buffer))^, numBytes);