int sockfd = socket ( AF_INET , SOCK_STREAM , 0 ) ; // IPv4 struct sockaddr_in server_addr ; bzero ( & server_addr , sizeof ( server_addr ) ) ; server_addr . sin_family = AF_INET ; const char * ip = "127.0.0.1" ; server_addr . sin_addr . s_addr = inet_addr ( ip ) ; server_addr . sin_port = htons ( 1234 ) ; //port int err_log = connect ( sockfd , ( struct sockaddr * ) & server_addr , sizeof ( server_addr ) ) ; if ( err_log != 0 ) perror ( "connect" ) ; close ( sockfd ) ; return - 1 ; // message string pre = "POST /home/ubuntu/ HTTP/1.1\r\n" "Host: 127.0.0.1:1234\r\n" "Content-Type: application/json\r\n" "Content-Length: " ; string json = "{\"item1\":\"val1\", \"item2\":6, \"image_nums\":[" ; ifstream ifs ( "image.txt" ) ; int tmp ; while ( ifs >> tmp ) { if ( ifs . eof ( ) ) break ; string ss = to_string ( tmp ) ; json += ss + "," ; ifs . close ( ) ; json = json . substr ( 0 , json . length ( ) - 1 ) + "]" + "}" ; pre += to_string ( json . length ( ) ) + "\r\n\r\n" + json ; int send_ret = write ( sockfd , pre . c_str ( ) , pre . size ( ) ) ; cout << "send " << send_ret << endl ; // response char recv_buf [ 8 * 1024 ] = { 0 } ; recv ( sockfd , recv_buf , sizeof ( recv_buf ) , 0 ) ; FILE * fd = fopen ( "response.json" , "wb+" ) ; fwrite ( recv_buf , 1 , bytes_received , fd ) ; fclose ( fd ) ; close ( sockfd ) ; return 0 ;