DIRECTORYOISCPTypes USING [ExchangeClientType, ExchangeID, maxDataBytePerExchange, WaitTime],PrincOps USING [ByteBltBlock],NSAddress USING [NetworkAddress, SocketNumber];PacketExchange: DEFINITIONS = BEGINBlock: TYPE = PrincOps.ByteBltBlock;ExchangeHandle: TYPE  = REF PacketExchangeObject;PacketExchangeObject: TYPE;RequestHandle: TYPE = REF RequestObject;  -- returned by WaitForRequestRequestObject: TYPE = RECORD [nBytes: CARDINAL,  -- the byte size of the request BlockrequestType: OISCPTypes.ExchangeClientType,requestersExchangeID: PRIVATE OISCPTypes.ExchangeID,requestersAddress: PRIVATE NSAddress.NetworkAddress]; maxBlockLength: CARDINAL = OISCPTypes.maxDataBytePerExchange; -- in bytesErrorReason: TYPE = {blockTooBig, blockTooSmall, noDestinationSocket,noRouteToDestination, hardwareProblem, aborted, timeout};defaultWaitTime: OISCPTypes.WaitTime = 60000; -- in msecsError: ERROR [why: ErrorReason];Timeout: SIGNAL; -- this may be RESUMEdCreateRequestor: PROCEDURE [waitTime: OISCPTypes.WaitTime _ defaultWaitTime] RETURNS [ExchangeHandle]; -- at any socket numberSendRequest: PUBLIC PROCEDURE [h: ExchangeHandle, remote: NSAddress.NetworkAddress,requestBlk, replyBlk: Block,requestType: OISCPTypes.ExchangeClientType _ unspecified]RETURNS [nBytes: CARDINAL, replyType: OISCPTypes.ExchangeClientType];CreateReplyer: PROCEDURE [localSocket: NSAddress.SocketNumber,requestCount: CARDINAL _ 1, waitTime: OISCPTypes.WaitTime _ defaultWaitTime]RETURNS [ExchangeHandle]; -- requestCount is estimate of number of "to be queued" requestsWaitForRequest: PROCEDURE [h: ExchangeHandle, requestBlk: Block,requiredRequestType: OISCPTypes.ExchangeClientType _ unspecified]RETURNS [rH: RequestHandle];SendReply: PUBLIC PROCEDURE [h: ExchangeHandle, rH: RequestHandle, replyBlk: Block, replyType: OISCPTypes.ExchangeClientType _ unspecified];Delete: PROCEDURE [h: ExchangeHandle];SetWaitTime: PROCEDURE [h: ExchangeHandle, waitTime: OISCPTypes.WaitTime];END.\199b14B25i611I78i31I51i39I46i80I108i1I63i11I180i11I1i36bI5B27i1bI7B9i25t10 31bI15B12t0 50t10 9t0 14t10 1t0 1i24I1b12B246t10i16bI13B1i1I24t0 14t10 42t0 49t10 13t0 14t10 1t0 1i65I2i45bI14B162i52I3b9B144i69t10bI6B16t0 14t10 1t0 2t10b11B13t0 48t10 3t0LOGTime: October 23, 1980  1:50 PM  By: Dalal  Action: created file.Time: January 13, 1981  5:01 PM  By: BLyon  Action: moved file to Pilot Communication.\1i  ì  PacketExchange.mesaCopyright c 1985 by Xerox Corporation.  All rights reserved.BLyon on: January 20, 1981  3:00 PMThe Packet Exchange Protocol is a request/reply protocol that provides a little morereliability than raw packets transmitetd from a socket, and less reliabilty than theSequenced Packet Protocol.  Usually one end will provide some service at awell known socket or at a network address that is available through a bindingprocess involving the Clearinghouse.  The other end acquires a socket and sends arequest.  The request will be retransmitted a number of times with the intervalbetween retransmissions based on the delay to the remote entity.definitionstypes and constants.the next to fields are used in the reply;  clients should not touch these.interfaceerrors and signalsproceduresthe requestorthe replyeruser must save rH inorder to send a replyupon success return of SendReply, rH is invalid.  request and reply can both point to the same piece of storage. Ê”  ˜ codešœ™Kšœ
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