Error Handling In Network Programming
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R Programming Error Handling
network timeouts More like this Master Merlin's new I/O classes Programming Java threads in the real world, Part 9 Programming Java threads in the real world, Part 9 Learn just how easy it is to prevent stalled clients and servers Email a friend To Use commas to separate multiple email addresses From Privacy Policy Thank you Your message has been sent. Sorry There was an error emailing this page. Comments By David Reilly JavaWorld | Sep 1, 1999 1:00 AM PT RELATED TOPICS Core Java Comments Many programmers dread the thought of handling network timeouts. A common fear is that a simple, single-threaded network client without timeout support will balloon into a complex multithreaded nightmare, with separate threads needed to detect network timeouts, and some form of notification process at work between
known as exception handling). By convention, the programmer is expected to prevent errors from occurring in the first place, and test return values from functions.
Posix Signal Handling In Network Programming
For example, -1 and NULL are used in several functions such as exception programming socket() (Unix socket programming) or malloc() respectively to indicate problems that the programmer should be aware about. In exception programming topics a worst case scenario where there is an unavoidable error and no way to recover from it, a C programmer usually tries to log the error and "gracefully" terminate http://www.javaworld.com/javaworld/jw-09-1999/jw-09-timeout.html the program. There is an external variable called "errno", accessible by the programs after including
Class Creating a TCP Server Exception Handling: Socket-Specific Exceptions Summary ⎙ Print + Share This Page 1 of 9 Next > Discover how to utilize the connection between TCP and the Java socket API to provide a clear http://www.informit.com/articles/article.aspx?p=27633&seqNum=9 and easy mechanism for networking. This chapter is from the book This chapter is http://www.java2s.com/Code/Python/Network/ErrorHandlingExample.htm from the book Java™ Network Programming and Distributed Computing Learn More Buy This chapter is from the book This chapter is from the book Java™ Network Programming and Distributed Computing Learn More Buy The Transmission Control Protocol (TCP) is a stream-based method of network communication that is far different from any discussed previously. This chapter discusses TCP streams and error handling how they operate under Java. 6.1 Overview TCP provides an interface to network communications that is radically different from the User Datagram Protocol (UDP) discussed in Chapter 5. The properties of TCP make it highly attractive to network programmers, as it simplifies network communication by removing many of the obstacles of UDP, such as ordering of packets and packet loss. While UDP is concerned with the transmission of packets of data, TCP focuses instead on establishing programming error handling a network connection, through which a stream of bytes may be sent and received. In Chapter 5 we saw that packets may be sent through a network using various paths and may arrive at different times. This benefits performance and robustness, as the loss of a single packet doesn't necessarily disrupt the transmission of other packets. Nonetheless, such a system creates extra work for programmers who need to guarantee delivery of data. TCP eliminates this extra work by guaranteeing delivery and order, providing for a reliable byte communication stream between client and server that supports two-way communication. It establishes a "virtual connection" between two machines, through which streams of data may be sent (see Figure 6-1). Figure 6-1 TCP establishes a virtual connection to transmit data. TCP uses a lower-level communications protocol, the Internet Protocol (IP), to establish the connection between machines. This connection provides an interface that allows streams of bytes to be sent and received, and transparently converts the data into IP datagram packets. A common problem with datagrams, as we saw in Chapter 5, is that they do not guarantee that packets arrive at their destination. TCP takes care of this problem. It provides guaranteed delivery of bytes of data. Of course, it's always possible that network errors will prevent delivery, but TCP handles the implementation issues such as resending packets
Error HandleError Handling Example import socket, sys host = sys.argv[1] textport = sys.argv[2] filename = sys.argv[3] try: s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) except socket.error, e: print "Strange error creating socket: %s" % e sys.exit(1) try: port = int(textport) except ValueError: print "Couldn't find your port: %s" % e sys.exit(1) try: s.connect((host, port)) except socket.gaierror, e: print "Address-related error connecting to server: %s" % e sys.exit(1) except socket.error, e: print "Connection error: %s" % e sys.exit(1) try: s.sendall("GET %s HTTP/1.0\r\n\r\n" % filename) except socket.error, e: print "Error sending data: %s" % e sys.exit(1) while 1: try: buf = s.recv(2048) except socket.error, e: print "Error receiving data: %s" % e sys.exit(1) if not len(buf): break sys.stdout.write(buf) Related examples in the same category1.Create handler for socket handler2.Server With Error Handlingjava2s.com |Email:info at java2s.com|© Demo Source and Support. All rights reserved.