本文中， 我们继续来做小实验， 看看linux单进程能打开的最大的句柄数（其实也是文件数， 因为linux下一切皆文件嘛）, 命令如下：
xxxxxx:~/network> ulimit -a
core file size (blocks, -c) unlimited
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 28064
max locked memory (kbytes, -l) 32
max memory size (kbytes, -m) unlimited
open files (-n) 1024
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 28064
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
xxxxxx:~/network>
xxxxxx:~/network>
xxxxxx:~/network>
xxxxxx:~/network> ulimit -n
1024
xxxxxx:~/network>
#include <malloc.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/ioctl.h>
#include <stdarg.h>
#include <fcntl.h>
#include <fcntl.h>
int main()
{
int iSock = 0;
for(unsigned int i = 0; i < 1050; i++)
{
iSock = socket(AF_INET, SOCK_DGRAM, 0); // 模拟句柄泄漏
printf("iSock is %d\n", iSock);
}
printf("end\n");
return 0;
}
xxxxxx:~/network> ./a.out
iSock is 3
iSock is 4
iSock is 5
iSock is 6
iSock is 7
iSock is 8
iSock is 9
iSock is 10
iSock is 11
iSock is 12
iSock is 13
iSock is 14
iSock is 15
iSock is 16
iSock is 17
iSock is 18
iSock is 19
iSock is 20
iSock is 21
iSock is 22
iSock is 23
iSock is 24
iSock is 25
iSock is 26
iSock is 27
iSock is 28
iSock is 29
iSock is 30
iSock is 31
iSock is 32
iSock is 33
iSock is 34
iSock is 35
iSock is 36
iSock is 37
iSock is 38
iSock is 39
iSock is 40
iSock is 41
iSock is 42
iSock is 43
iSock is 44
iSock is 45
iSock is 46
iSock is 47
iSock is 48
iSock is 49
iSock is 50
iSock is 51
iSock is 52
iSock is 53
iSock is 54
iSock is 55
iSock is 56
iSock is 57
iSock is 58
iSock is 59
iSock is 60
iSock is 61
iSock is 62
iSock is 63
iSock is 64
iSock is 65
iSock is 66
iSock is 67
iSock is 68
iSock is 69
iSock is 70
iSock is 71
iSock is 72
iSock is 73
iSock is 74
iSock is 75
iSock is 76
iSock is 77
iSock is 78
iSock is 79
iSock is 80
iSock is 81
iSock is 82
iSock is 83
iSock is 84
iSock is 85
iSock is 86
iSock is 87
iSock is 88
iSock is 89
iSock is 90
iSock is 91
iSock is 92
iSock is 93
iSock is 94
iSock is 95
iSock is 96
iSock is 97
iSock is 98
iSock is 99
iSock is 100
iSock is 101
iSock is 102
iSock is 103
iSock is 104
iSock is 105
iSock is 106
iSock is 107
iSock is 108
iSock is 109
iSock is 110
iSock is 111
iSock is 112
iSock is 113
iSock is 114
iSock is 115
iSock is 116
iSock is 117
iSock is 118
iSock is 119
iSock is 120
iSock is 121
iSock is 122
iSock is 123
iSock is 124
iSock is 125
iSock is 126
iSock is 127
iSock is 128
iSock is 129
iSock is 130
iSock is 131
iSock is 132
iSock is 133
iSock is 134
iSock is 135
iSock is 136
iSock is 137
iSock is 138
iSock is 139
iSock is 140
iSock is 141
iSock is 142
iSock is 143
iSock is 144
iSock is 145
iSock is 146
iSock is 147
iSock is 148
iSock is 149
iSock is 150
iSock is 151
iSock is 152
iSock is 153
iSock is 154
iSock is 155
iSock is 156
iSock is 157
iSock is 158
iSock is 159
iSock is 160
iSock is 161
iSock is 162
iSock is 163
iSock is 164
iSock is 165
iSock is 166
iSock is 167
iSock is 168
iSock is 169
iSock is 170
iSock is 171
iSock is 172
iSock is 173
iSock is 174
iSock is 175
iSock is 176
iSock is 177
iSock is 178
iSock is 179
iSock is 180
iSock is 181
iSock is 182
iSock is 183
iSock is 184
iSock is 185
iSock is 186
iSock is 187
iSock is 188
iSock is 189
iSock is 190
iSock is 191
iSock is 192
iSock is 193
iSock is 194
iSock is 195
iSock is 196
iSock is 197
iSock is 198
iSock is 199
iSock is 200
iSock is 201
iSock is 202
iSock is 203
iSock is 204
iSock is 205
iSock is 206
iSock is 207
iSock is 208
iSock is 209
iSock is 210
iSock is 211
iSock is 212
iSock is 213
iSock is 214
iSock is 215
iSock is 216
iSock is 217
iSock is 218
iSock is 219
iSock is 220
iSock is 221
iSock is 222
iSock is 223
iSock is 224
iSock is 225
iSock is 226
iSock is 227
iSock is 228
iSock is 229
iSock is 230
iSock is 231
iSock is 232
iSock is 233
iSock is 234
iSock is 235
iSock is 236
iSock is 237
iSock is 238
iSock is 239
iSock is 240
iSock is 241
iSock is 242
iSock is 243
iSock is 244
iSock is 245
iSock is 246
iSock is 247
iSock is 248
iSock is 249
iSock is 250
iSock is 251
iSock is 252
iSock is 253
iSock is 254
iSock is 255
iSock is 256
iSock is 257
iSock is 258
iSock is 259
iSock is 260
iSock is 261
iSock is 262
iSock is 263
iSock is 264
iSock is 265
iSock is 266
iSock is 267
iSock is 268
iSock is 269
iSock is 270
iSock is 271
iSock is 272
iSock is 273
iSock is 274
iSock is 275
iSock is 276
iSock is 277
iSock is 278
iSock is 279
iSock is 280
iSock is 281
iSock is 282
iSock is 283
iSock is 284
iSock is 285
iSock is 286
iSock is 287
iSock is 288
iSock is 289
iSock is 290
iSock is 291
iSock is 292
iSock is 293
iSock is 294
iSock is 295
iSock is 296
iSock is 297
iSock is 298
iSock is 299
iSock is 300
iSock is 301
iSock is 302
iSock is 303
iSock is 304
iSock is 305
iSock is 306
iSock is 307
iSock is 308
iSock is 309
iSock is 310
iSock is 311
iSock is 312
iSock is 313
iSock is 314
iSock is 315
iSock is 316
iSock is 317
iSock is 318
iSock is 319
iSock is 320
iSock is 321
iSock is 322
iSock is 323
iSock is 324
iSock is 325
iSock is 326
iSock is 327
iSock is 328
iSock is 329
iSock is 330
iSock is 331
iSock is 332
iSock is 333
iSock is 334
iSock is 335
iSock is 336
iSock is 337
iSock is 338
iSock is 339
iSock is 340
iSock is 341
iSock is 342
iSock is 343
iSock is 344
iSock is 345
iSock is 346
iSock is 347
iSock is 348
iSock is 349
iSock is 350
iSock is 351
iSock is 352
iSock is 353
iSock is 354
iSock is 355
iSock is 356
iSock is 357
iSock is 358
iSock is 359
iSock is 360
iSock is 361
iSock is 362
iSock is 363
iSock is 364
iSock is 365
iSock is 366
iSock is 367
iSock is 368
iSock is 369
iSock is 370
iSock is 371
iSock is 372
iSock is 373
iSock is 374
iSock is 375
iSock is 376
iSock is 377
iSock is 378
iSock is 379
iSock is 380
iSock is 381
iSock is 382
iSock is 383
iSock is 384
iSock is 385
iSock is 386
iSock is 387
iSock is 388
iSock is 389
iSock is 390
iSock is 391
iSock is 392
iSock is 393
iSock is 394
iSock is 395
iSock is 396
iSock is 397
iSock is 398
iSock is 399
iSock is 400
iSock is 401
iSock is 402
iSock is 403
iSock is 404
iSock is 405
iSock is 406
iSock is 407
iSock is 408
iSock is 409
iSock is 410
iSock is 411
iSock is 412
iSock is 413
iSock is 414
iSock is 415
iSock is 416
iSock is 417
iSock is 418
iSock is 419
iSock is 420
iSock is 421
iSock is 422
iSock is 423
iSock is 424
iSock is 425
iSock is 426
iSock is 427
iSock is 428
iSock is 429
iSock is 430
iSock is 431
iSock is 432
iSock is 433
iSock is 434
iSock is 435
iSock is 436
iSock is 437
iSock is 438
iSock is 439
iSock is 440
iSock is 441
iSock is 442
iSock is 443
iSock is 444
iSock is 445
iSock is 446
iSock is 447
iSock is 448
iSock is 449
iSock is 450
iSock is 451
iSock is 452
iSock is 453
iSock is 454
iSock is 455
iSock is 456
iSock is 457
iSock is 458
iSock is 459
iSock is 460
iSock is 461
iSock is 462
iSock is 463
iSock is 464
iSock is 465
iSock is 466
iSock is 467
iSock is 468
iSock is 469
iSock is 470
iSock is 471
iSock is 472
iSock is 473
iSock is 474
iSock is 475
iSock is 476
iSock is 477
iSock is 478
iSock is 479
iSock is 480
iSock is 481
iSock is 482
iSock is 483
iSock is 484
iSock is 485
iSock is 486
iSock is 487
iSock is 488
iSock is 489
iSock is 490
iSock is 491
iSock is 492
iSock is 493
iSock is 494
iSock is 495
iSock is 496
iSock is 497
iSock is 498
iSock is 499
iSock is 500
iSock is 501
iSock is 502
iSock is 503
iSock is 504
iSock is 505
iSock is 506
iSock is 507
iSock is 508
iSock is 509
iSock is 510
iSock is 511
iSock is 512
iSock is 513
iSock is 514
iSock is 515
iSock is 516
iSock is 517
iSock is 518
iSock is 519
iSock is 520
iSock is 521
iSock is 522
iSock is 523
iSock is 524
iSock is 525
iSock is 526
iSock is 527
iSock is 528
iSock is 529
iSock is 530
iSock is 531
iSock is 532
iSock is 533
iSock is 534
iSock is 535
iSock is 536
iSock is 537
iSock is 538
iSock is 539
iSock is 540
iSock is 541
iSock is 542
iSock is 543
iSock is 544
iSock is 545
iSock is 546
iSock is 547
iSock is 548
iSock is 549
iSock is 550
iSock is 551
iSock is 552
iSock is 553
iSock is 554
iSock is 555
iSock is 556
iSock is 557
iSock is 558
iSock is 559
iSock is 560
iSock is 561
iSock is 562
iSock is 563
iSock is 564
iSock is 565
iSock is 566
iSock is 567
iSock is 568
iSock is 569
iSock is 570
iSock is 571
iSock is 572
iSock is 573
iSock is 574
iSock is 575
iSock is 576
iSock is 577
iSock is 578
iSock is 579
iSock is 580
iSock is 581
iSock is 582
iSock is 583
iSock is 584
iSock is 585
iSock is 586
iSock is 587
iSock is 588
iSock is 589
iSock is 590
iSock is 591
iSock is 592
iSock is 593
iSock is 594
iSock is 595
iSock is 596
iSock is 597
iSock is 598
iSock is 599
iSock is 600
iSock is 601
iSock is 602
iSock is 603
iSock is 604
iSock is 605
iSock is 606
iSock is 607
iSock is 608
iSock is 609
iSock is 610
iSock is 611
iSock is 612
iSock is 613
iSock is 614
iSock is 615
iSock is 616
iSock is 617
iSock is 618
iSock is 619
iSock is 620
iSock is 621
iSock is 622
iSock is 623
iSock is 624
iSock is 625
iSock is 626
iSock is 627
iSock is 628
iSock is 629
iSock is 630
iSock is 631
iSock is 632
iSock is 633
iSock is 634
iSock is 635
iSock is 636
iSock is 637
iSock is 638
iSock is 639
iSock is 640
iSock is 641
iSock is 642
iSock is 643
iSock is 644
iSock is 645
iSock is 646
iSock is 647
iSock is 648
iSock is 649
iSock is 650
iSock is 651
iSock is 652
iSock is 653
iSock is 654
iSock is 655
iSock is 656
iSock is 657
iSock is 658
iSock is 659
iSock is 660
iSock is 661
iSock is 662
iSock is 663
iSock is 664
iSock is 665
iSock is 666
iSock is 667
iSock is 668
iSock is 669
iSock is 670
iSock is 671
iSock is 672
iSock is 673
iSock is 674
iSock is 675
iSock is 676
iSock is 677
iSock is 678
iSock is 679
iSock is 680
iSock is 681
iSock is 682
iSock is 683
iSock is 684
iSock is 685
iSock is 686
iSock is 687
iSock is 688
iSock is 689
iSock is 690
iSock is 691
iSock is 692
iSock is 693
iSock is 694
iSock is 695
iSock is 696
iSock is 697
iSock is 698
iSock is 699
iSock is 700
iSock is 701
iSock is 702
iSock is 703
iSock is 704
iSock is 705
iSock is 706
iSock is 707
iSock is 708
iSock is 709
iSock is 710
iSock is 711
iSock is 712
iSock is 713
iSock is 714
iSock is 715
iSock is 716
iSock is 717
iSock is 718
iSock is 719
iSock is 720
iSock is 721
iSock is 722
iSock is 723
iSock is 724
iSock is 725
iSock is 726
iSock is 727
iSock is 728
iSock is 729
iSock is 730
iSock is 731
iSock is 732
iSock is 733
iSock is 734
iSock is 735
iSock is 736
iSock is 737
iSock is 738
iSock is 739
iSock is 740
iSock is 741
iSock is 742
iSock is 743
iSock is 744
iSock is 745
iSock is 746
iSock is 747
iSock is 748
iSock is 749
iSock is 750
iSock is 751
iSock is 752
iSock is 753
iSock is 754
iSock is 755
iSock is 756
iSock is 757
iSock is 758
iSock is 759
iSock is 760
iSock is 761
iSock is 762
iSock is 763
iSock is 764
iSock is 765
iSock is 766
iSock is 767
iSock is 768
iSock is 769
iSock is 770
iSock is 771
iSock is 772
iSock is 773
iSock is 774
iSock is 775
iSock is 776
iSock is 777
iSock is 778
iSock is 779
iSock is 780
iSock is 781
iSock is 782
iSock is 783
iSock is 784
iSock is 785
iSock is 786
iSock is 787
iSock is 788
iSock is 789
iSock is 790
iSock is 791
iSock is 792
iSock is 793
iSock is 794
iSock is 795
iSock is 796
iSock is 797
iSock is 798
iSock is 799
iSock is 800
iSock is 801
iSock is 802
iSock is 803
iSock is 804
iSock is 805
iSock is 806
iSock is 807
iSock is 808
iSock is 809
iSock is 810
iSock is 811
iSock is 812
iSock is 813
iSock is 814
iSock is 815
iSock is 816
iSock is 817
iSock is 818
iSock is 819
iSock is 820
iSock is 821
iSock is 822
iSock is 823
iSock is 824
iSock is 825
iSock is 826
iSock is 827
iSock is 828
iSock is 829
iSock is 830
iSock is 831
iSock is 832
iSock is 833
iSock is 834
iSock is 835
iSock is 836
iSock is 837
iSock is 838
iSock is 839
iSock is 840
iSock is 841
iSock is 842
iSock is 843
iSock is 844
iSock is 845
iSock is 846
iSock is 847
iSock is 848
iSock is 849
iSock is 850
iSock is 851
iSock is 852
iSock is 853
iSock is 854
iSock is 855
iSock is 856
iSock is 857
iSock is 858
iSock is 859
iSock is 860
iSock is 861
iSock is 862
iSock is 863
iSock is 864
iSock is 865
iSock is 866
iSock is 867
iSock is 868
iSock is 869
iSock is 870
iSock is 871
iSock is 872
iSock is 873
iSock is 874
iSock is 875
iSock is 876
iSock is 877
iSock is 878
iSock is 879
iSock is 880
iSock is 881
iSock is 882
iSock is 883
iSock is 884
iSock is 885
iSock is 886
iSock is 887
iSock is 888
iSock is 889
iSock is 890
iSock is 891
iSock is 892
iSock is 893
iSock is 894
iSock is 895
iSock is 896
iSock is 897
iSock is 898
iSock is 899
iSock is 900
iSock is 901
iSock is 902
iSock is 903
iSock is 904
iSock is 905
iSock is 906
iSock is 907
iSock is 908
iSock is 909
iSock is 910
iSock is 911
iSock is 912
iSock is 913
iSock is 914
iSock is 915
iSock is 916
iSock is 917
iSock is 918
iSock is 919
iSock is 920
iSock is 921
iSock is 922
iSock is 923
iSock is 924
iSock is 925
iSock is 926
iSock is 927
iSock is 928
iSock is 929
iSock is 930
iSock is 931
iSock is 932
iSock is 933
iSock is 934
iSock is 935
iSock is 936
iSock is 937
iSock is 938
iSock is 939
iSock is 940
iSock is 941
iSock is 942
iSock is 943
iSock is 944
iSock is 945
iSock is 946
iSock is 947
iSock is 948
iSock is 949
iSock is 950
iSock is 951
iSock is 952
iSock is 953
iSock is 954
iSock is 955
iSock is 956
iSock is 957
iSock is 958
iSock is 959
iSock is 960
iSock is 961
iSock is 962
iSock is 963
iSock is 964
iSock is 965
iSock is 966
iSock is 967
iSock is 968
iSock is 969
iSock is 970
iSock is 971
iSock is 972
iSock is 973
iSock is 974
iSock is 975
iSock is 976
iSock is 977
iSock is 978
iSock is 979
iSock is 980
iSock is 981
iSock is 982
iSock is 983
iSock is 984
iSock is 985
iSock is 986
iSock is 987
iSock is 988
iSock is 989
iSock is 990
iSock is 991
iSock is 992
iSock is 993
iSock is 994
iSock is 995
iSock is 996
iSock is 997
iSock is 998
iSock is 999
iSock is 1000
iSock is 1001
iSock is 1002
iSock is 1003
iSock is 1004
iSock is 1005
iSock is 1006
iSock is 1007
iSock is 1008
iSock is 1009
iSock is 1010
iSock is 1011
iSock is 1012
iSock is 1013
iSock is 1014
iSock is 1015
iSock is 1016
iSock is 1017
iSock is 1018
iSock is 1019
iSock is 1020
iSock is 1021
iSock is 1022
iSock is 1023
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
iSock is -1
end
xxxxxx:~/network>
句柄有限， 请你珍惜。
另外要注意的是， 这个1024并不是固定的， 在不同的机器上还不一样， 我另外找了一台机器进行测试， 发现这个值远远大于1024, 如
yyyyyy$ ulimit -n
100001