1
我試圖將文件從發件人傳輸到接收方，使數據包在途中沒有分段。它由兩個任務組成：（1）找出從發送方到接收方的路徑上最小MTU的最大分片單元（MTU），（2）然後以不超過最小MTU的分組傳輸文件在接收和發送主機之間。傳輸帶有套接字的文件，並找到最大MTU
，我有到接收器的代碼是：
# ---- Imports ---- #
from socket import *
import sys, struct, time
# ---- Constants ---- #
HOST = ""
PORT = 5555
ADDRESS = (HOST,PORT)
PORT_MSGS = 9999
TIMEOUT = 0.0005
BUFFER = 65536
#--- Body --- #
mtu = 0
numMsgs = 0
#make a socket
try:
sckt = socket(AF_INET,SOCK_DGRAM)
sckt.bind(ADDRESS)
sckt.settimeout(TIMEOUT)
except socket.error:
if sckt:
sckt.close() # Socket Creation Failed
sys.exit(1) # Exit program with error
#get mtu and number of messages
header = struct.pack('c','k')
while (1):
try:
data, addr = sckt.recvfrom(BUFFER)
char = struct.unpack('lc', data[0:5])[1]
if (char == 'm'):
mtu = struct.unpack('lc', data[0:5])[0]
numMsgs = int(data[5:])
#send ack for the mtu message
sckt.sendto(header, (addr[0] ,PORT_MSGS))
break
if not(char == 'm'):
continue
except socket.error:
continue
except timeout:
continue
mtuFileName = sys.argv[1]
fileName= sys.argv[2]
#make mtu file
mtuFile = open(mtuFileName,'wb')
mtuFile.write(str(mtu))
mtuFile.close()
f = open(fileName,'wb')
packetsBuffer = numMsgs * [0]
# Receive messages
packetCounter = 0
data, addr = sckt.recvfrom(BUFFER)
while (1):
packetSeq = int(struct.unpack('lc', data[0:5])[0])
char = struct.unpack('lc', data[0:5])[1]
if (char == 'r') and (packetsBuffer[packetSeq] == 0):
dataOfPack = data[5:]
packetsBuffer[packetSeq] = dataOfPack
packetCounter = packetCounter + 1
if(numMsgs == packetCounter):
break
data, addr = sckt.recvfrom(BUFFER)
#write messages to file
buffIndex = 0
while (buffIndex < numMsgs):
f.write(packetsBuffer[buffIndex])
buffIndex = buffIndex + 1
f.close()
sckt.close() # close the socket
發件人是：
# ------- Imports ------- #
from socket import *
import sys, struct, os, stat, commands, time
# ------- Constants ------- #
PORT_SEND = 5555
IP_HOST = sys.argv[1]
SERVER_ADDRESS = (IP_HOST ,PORT_SEND)
MY_PORT = 9999
MAX_FAILS_SENDING = 10
MTU_DISCOVERY_SEQ = 0 # the Sequence number sending MTU discovery messages
TIMEOUT = 0.0005
BUFFER = 65536
# ------- Body ------- #
#socket- file
try:
scktFile = socket(AF_INET,SOCK_DGRAM)
scktFile.connect(SERVER_ADDRESS)
scktFile.settimeout(TIMEOUT)
except socket.error:
if scktFile:
scktFile.close() # Socket Creation Failed
sys.exit(1) # Exit program with error
#socket- ack/mtu
try:
scktMsgs = socket(AF_INET,SOCK_DGRAM)
scktMsgs.bind(("", MY_PORT))
scktMsgs.settimeout(TIMEOUT)
except socket.error:
if scktMsgs:
scktMsgs.close() # Socket Creation Failed
sys.exit(1) # Exit program with error
#find the mtu
mtu = int(commands.getoutput(" tracepath "+sys.argv[1]+"| grep -i resume | awk '{print $3}'"))
payloadSize = mtu-(20+8+8+5)
fileName = sys.argv[2]
f = open (fileName, 'rb')
fileData = f.read(99999999)
fileLen = len(fileData)
numMsgs = fileLen/(payloadSize)
if((fileLen % payloadSize) != 0):
numMsgs = numMsgs + 1
#m - mtu,k - mtu ack, a - ack, f - fin, r - regular message part of file, w - wait for ack - after 10 rounds, n -name of file
while (1):
header = struct.pack('lc', mtu, 'm') #m - mtu
sNumMsgs = str(numMsgs)
scktFile.sendto(header+sNumMsgs, SERVER_ADDRESS)
try:
data,addr = scktFile.recvfrom(BUFFER)
char = struct.unpack('c', data[0])
if char == 'k':
break
except socket.error:
continue
except timeout:
continue
# send file content
seqNum = 0
header = struct.pack('lc', seqNum, 'r')#r - regular message part of file
while (1):
seqNum = 0
indexFile = 0
header = struct.pack('lc', seqNum, 'r')
data = fileData[indexFile:(indexFile+payloadSize)]
indexFile = indexFile + payloadSize
while (data):
if(scktFile.sendto(header+data,SERVER_ADDRESS)):
data = fileData[indexFile:(indexFile+payloadSize)]
indexFile = indexFile+payloadSize
#time.sleep(0.00005)
seqNum = seqNum + 1
seqNum = seqNum % numMsgs # Maximum Seq number
header = struct.pack('lc', seqNum, 'r')
if seqNum == 0:
break
scktMsgs.close()
scktFile.close()
我不斷收到錯誤 「0分（無輸出）」 和我不知道爲什麼