Objective-C

Receive a 4-byte Length Prefix from a Socket

Demonstrates Socket.ReceiveCount, which reads a four-byte length prefix as a signed 32-bit integer. A return value of -1 indicates failure.

Background. Reading the length prefix first tells the application exactly how many bytes to read for the message body, which is a reliable way to know when a full message has arrived.

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Objective-C

#import <CkoSocket.h>

BOOL success = NO;

CkoSocket *socket = [[CkoSocket alloc] init];

//  Connect to the server using TLS.
BOOL bTls = YES;
int maxWaitMs = 5000;
success = [socket Connect: @"example.com" port: [NSNumber numberWithInt: 5000] ssl: bTls maxWaitMs: [NSNumber numberWithInt: maxWaitMs]];
if (success == NO) {
    NSLog(@"%@",socket.LastErrorText);
    return;
}

//  Read a four-byte length prefix as a signed 32-bit integer (network byte order by default).  A
//  return value of -1 indicates failure.
int messageLength = [[socket ReceiveCount] intValue];
if (messageLength < 0) {
    NSLog(@"%@",socket.LastErrorText);
    return;
}

NSLog(@"%@%d%@",@"The peer will send ",messageLength,@" bytes.");