Objective-C

Get Received SSH Bytes into a BinData

Demonstrates the Chilkat Ssh.GetReceivedBd method, which appends the bytes currently in a channel's normal receive buffer to a BinData. The first argument is the channel number and the second is the BinData. The channel receive buffer is cleared afterward; existing bytes in the BinData are preserved.

Background: When the remote command emits binary — a tarball, an image, a compressed stream — decoding it as text through a charset would corrupt it. BinData keeps the bytes exactly as received, so you can write them to a file, hash them, or hand them to another API. Like the StringBuilder form it appends, making it easy to accumulate across successive reads. On failure the BinData is left unchanged.

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Objective-C

#import <CkoSsh.h>
#import <NSString.h>
#import <CkoBinData.h>

BOOL success = NO;

//  Demonstrates the Ssh.GetReceivedBd method, which appends the bytes currently in a channel's
//  receive buffer to a BinData.  The 1st argument is the channel number and the 2nd is the
//  BinData.  The channel receive buffer is cleared afterward.

CkoSsh *ssh = [[CkoSsh alloc] init];

int sshPort = 22;
success = [ssh Connect: @"ssh.example.com" port: [NSNumber numberWithInt: sshPort]];
if (success == NO) {
    NSLog(@"%@",ssh.LastErrorText);
    return;
}

//  Normally you would not hard-code the password in source.  You should instead obtain it
//  from an interactive prompt, environment variable, or a secrets vault.
NSString *password = @"mySshPassword";

success = [ssh AuthenticatePw: @"mySshLogin" password: password];
if (success == NO) {
    NSLog(@"%@",ssh.LastErrorText);
    return;
}

int channelNum = [[ssh OpenSessionChannel] intValue];
if (channelNum < 0) {
    NSLog(@"%@",ssh.LastErrorText);
    return;
}

//  Run a command whose output may be binary.
success = [ssh SendReqExec: [NSNumber numberWithInt: channelNum] command: @"cat /usr/bin/hostname"];
if (success == NO) {
    NSLog(@"%@",ssh.LastErrorText);
    return;
}

//  IMPORTANT: Set a read timeout.  ReadTimeoutMs defaults to 0, which means no limit -- without
//  it, this call waits forever if the server never sends channel close.
ssh.ReadTimeoutMs = [NSNumber numberWithInt:15000];

success = [ssh ChannelReceiveToClose: [NSNumber numberWithInt: channelNum]];
if (success == NO) {
    NSLog(@"%@",ssh.LastErrorText);
    return;
}

//  Append the raw received bytes to a BinData.  Existing bytes in the BinData are preserved.
CkoBinData *bd = [[CkoBinData alloc] init];
success = [ssh GetReceivedBd: [NSNumber numberWithInt: channelNum] bd: bd];
if (success == NO) {
    NSLog(@"%@",ssh.LastErrorText);
    return;
}

NSLog(@"%@%d",@"Bytes received: ",[bd.NumBytes intValue]);

[ssh Disconnect];