Simple Socket Programming on iOS ARM64

Requirements:

Jailbroken iPhone with at least the following packages installed:

OpenSSH

Warm Up:

First, let’s start writing serversocket.c and clientsocket.c code:

/*
    C socket server example
*/

#include<stdio.h>
#include<string.h>    //strlen
#include<sys/socket.h>
#include<arpa/inet.h>    //inet_addr
#include<unistd.h>    //write

int main(int argc , char *argv[])
{
    int socket_desc , client_sock , c , read_size;
    struct sockaddr_in server , client;
    char client_message[2000];
    
    //Create socket
    socket_desc = socket(AF_INET , SOCK_STREAM , 0);
    if (socket_desc == -1)
    {
        printf("Could not create socket");
    }
    puts("Socket created");
    
    //Prepare the sockaddr_in structure
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons( 8888 );
    
    //Bind
    if( bind(socket_desc,(struct sockaddr *)&server , sizeof(server)) < 0)
    {
        //print the error message

        perror("bind failed. Error");
        return 1;
    }
    puts("bind done");
    
    //Listen
    listen(socket_desc , 3);
    
    //Accept and incoming connection
    puts("Waiting for incoming connections...");
    c = sizeof(struct sockaddr_in);
    
    //accept connection from an incoming client
    client_sock = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c);
    if (client_sock < 0)
    {
        perror("accept failed");
        return 1;
    }
    puts("Connection accepted");
    
    //Receive a message from client
    while( (read_size = recv(client_sock , client_message , 2000 , 0)) > 0 )
    {
        //Send the message back to client
        write(client_sock , client_message , strlen(client_message));
    }
    
    if(read_size == 0)
    {
        puts("Client disconnected");
        fflush(stdout);
    }
    else if(read_size == -1)
    {
        perror("recv failed");
    }
    
    return 0;
}

/*
    C ECHO client example using sockets
*/
#include <stdio.h>    //printf
#include <string.h>    //strlen
#include <sys/socket.h>    //socket
#include <arpa/inet.h>    //inet_addr
#include <unistd.h>

int main(int argc , char *argv[])
{
    int sock;
    struct sockaddr_in server;
    char message[1000] , server_reply[2000];
    
    //Create socket
    sock = socket(AF_INET , SOCK_STREAM , 0);
    if (sock == -1)
    {
        printf("Could not create socket");
    }
    puts("Socket created");
    
    server.sin_addr.s_addr = inet_addr("192.168.0.22");
    server.sin_family = AF_INET;
    server.sin_port = htons( 8888 );

    //Connect to remote server
    if (connect(sock , (struct sockaddr *)&server , sizeof(server)) < 0)
    {
        perror("connect failed. Error");
        return 1;
    }
    
    puts("Connected\n");
    
    //keep communicating with server
    while(1)
    {
        printf("Enter message : ");
        scanf("%s" , message);
        
        //Send some data
        if( send(sock , message , strlen(message) , 0) < 0)
        {
            puts("Send failed");
            return 1;
        }
        
        //Receive a reply from the server
        
        if( recv(sock , server_reply , 2000 , 0) < 0)
        {
            puts("recv failed");
            break;
        }
        
        puts("Server reply :");
        puts(server_reply);
    }
    
    close(sock);
    return 0;
}

Action:

Now let’s compile them with the following command on MacOS:

clang -g clientsocket.c -o clientsocket -isysroot 

/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS14.4.sdk 

-arch arm64 -mios-version-min=9.0 -
 
clang -g serversocket.c -o serversocket

After compilation, transfer the “serversocket” binary into the iOS platform. After connecting to the phone via SSH, you should make it runnable and signed.

chmod +x serversocket

ldid -S serversocket

Knock out:

Now we can test our socket code on actual environment. Run serversocket on iOS and clientsocket on MacOS.

This hello socket program can be easily improved for transferring files and other purposes. As I said, food for thought.