So you’ve been using the SAP .NET Connector 3.0 for a while and it’s working great to connect your .NET application to SAP when suddenly you start getting this error:

**ERROR service '?' unknown**

You probably have some code like this (or you’re just trying to login or get your app to run):

Server = RfcServerManager.GetServer(serverName, rfcHandlers);

// other init...


So what happened? I’m guessing you have a new machine or recently removed some SAP-related software. I’m also guessing that if you install the SAP Logon pad, this issue will go away. But you don’t have to go to all that trouble! In my experience, all you need to do is add some configuration to the system services file. Here’s how:

  • Open Notepad as an administrator
  • Open this file: %windir%\system32\drivers\etc\services
  • Look around for services starting with “sap”
  • Assuming you don’t find much, add these lines to the end:
    sapdp00  3200/tcp
    sapdp01  3201/tcp
    sapdp02  3202/tcp
    sapdp03  3203/tcp
    sapdp04  3204/tcp
    sapdp05  3205/tcp
    sapdp06  3206/tcp
    sapdp07  3207/tcp
    sapdp08  3208/tcp
    sapdp09  3209/tcp
    sapdp10  3210/tcp
    sapdp11  3211/tcp
    sapdp12  3212/tcp
    sapdp13  3213/tcp
    sapdp14  3214/tcp
    sapdp15  3215/tcp
    sapdp16  3216/tcp
    sapdp17  3217/tcp
    sapdp18  3218/tcp
    sapdp19  3219/tcp
    sapdp20  3220/tcp
    sapdp21  3221/tcp
    sapdp22  3222/tcp
    sapdp23  3223/tcp
    sapdp24  3224/tcp
    sapdp25  3225/tcp
    sapdp26  3226/tcp
    sapdp27  3227/tcp
    sapdp28  3228/tcp
    sapdp29  3229/tcp
    sapdp30  3230/tcp
    sapdp31  3231/tcp
    sapdp32  3232/tcp
    sapdp33  3233/tcp
    sapdp34  3234/tcp
    sapdp35  3235/tcp
    sapdp36  3236/tcp
    sapdp37  3237/tcp
    sapdp38  3238/tcp
    sapdp39  3239/tcp
    sapdp40  3240/tcp
    sapdp41  3241/tcp
    sapdp42  3242/tcp
    sapdp43  3243/tcp
    sapdp44  3244/tcp
    sapdp45  3245/tcp
    sapdp46  3246/tcp
    sapdp47  3247/tcp
    sapdp48  3248/tcp
    sapdp49  3249/tcp
    sapdp50  3250/tcp
    sapdp51  3251/tcp
    sapdp52  3252/tcp
    sapdp53  3253/tcp
    sapdp54  3254/tcp
    sapdp55  3255/tcp
    sapdp56  3256/tcp
    sapdp57  3257/tcp
    sapdp58  3258/tcp
    sapdp59  3259/tcp
    sapdp60  3260/tcp
    sapdp61  3261/tcp
    sapdp62  3262/tcp
    sapdp63  3263/tcp
    sapdp64  3264/tcp
    sapdp65  3265/tcp
    sapdp66  3266/tcp
    sapdp67  3267/tcp
    sapdp68  3268/tcp
    sapdp69  3269/tcp
    sapdp70  3270/tcp
    sapdp71  3271/tcp
    sapdp72  3272/tcp
    sapdp73  3273/tcp
    sapdp74  3274/tcp
    sapdp75  3275/tcp
    sapdp76  3276/tcp
    sapdp77  3277/tcp
    sapdp78  3278/tcp
    sapdp79  3279/tcp
    sapdp80  3280/tcp
    sapdp81  3281/tcp
    sapdp82  3282/tcp
    sapdp83  3283/tcp
    sapdp84  3284/tcp
    sapdp85  3285/tcp
    sapdp86  3286/tcp
    sapdp87  3287/tcp
    sapdp88  3288/tcp
    sapdp89  3289/tcp
    sapdp90  3290/tcp
    sapdp91  3291/tcp
    sapdp92  3292/tcp
    sapdp93  3293/tcp
    sapdp94  3294/tcp
    sapdp95  3295/tcp
    sapdp96  3296/tcp
    sapdp97  3297/tcp
    sapdp98  3298/tcp
    sapdp99  3299/tcp
    sapgw00  3300/tcp
    sapgw01  3301/tcp
    sapgw02  3302/tcp
    sapgw03  3303/tcp
    sapgw04  3304/tcp
    sapgw05  3305/tcp
    sapgw06  3306/tcp
    sapgw07  3307/tcp
    sapgw08  3308/tcp
    sapgw09  3309/tcp
    sapgw10  3310/tcp
    sapgw11  3311/tcp
    sapgw12  3312/tcp
    sapgw13  3313/tcp
    sapgw14  3314/tcp
    sapgw15  3315/tcp
    sapgw16  3316/tcp
    sapgw17  3317/tcp
    sapgw18  3318/tcp
    sapgw19  3319/tcp
    sapgw20  3320/tcp
    sapgw21  3321/tcp
    sapgw22  3322/tcp
    sapgw23  3323/tcp
    sapgw24  3324/tcp
    sapgw25  3325/tcp
    sapgw26  3326/tcp
    sapgw27  3327/tcp
    sapgw28  3328/tcp
    sapgw29  3329/tcp
    sapgw30  3330/tcp
    sapgw31  3331/tcp
    sapgw32  3332/tcp
    sapgw33  3333/tcp
    sapgw34  3334/tcp
    sapgw35  3335/tcp
    sapgw36  3336/tcp
    sapgw37  3337/tcp
    sapgw38  3338/tcp
    sapgw39  3339/tcp
    sapgw40  3340/tcp
    sapgw41  3341/tcp
    sapgw42  3342/tcp
    sapgw43  3343/tcp
    sapgw44  3344/tcp
    sapgw45  3345/tcp
    sapgw46  3346/tcp
    sapgw47  3347/tcp
    sapgw48  3348/tcp
    sapgw49  3349/tcp
    sapgw50  3350/tcp
    sapgw51  3351/tcp
    sapgw52  3352/tcp
    sapgw53  3353/tcp
    sapgw54  3354/tcp
    sapgw55  3355/tcp
    sapgw56  3356/tcp
    sapgw57  3357/tcp
    sapgw58  3358/tcp
    sapgw59  3359/tcp
    sapgw60  3360/tcp
    sapgw61  3361/tcp
    sapgw62  3362/tcp
    sapgw63  3363/tcp
    sapgw64  3364/tcp
    sapgw65  3365/tcp
    sapgw66  3366/tcp
    sapgw67  3367/tcp
    sapgw68  3368/tcp
    sapgw69  3369/tcp
    sapgw70  3370/tcp
    sapgw71  3371/tcp
    sapgw72  3372/tcp
    sapgw73  3373/tcp
    sapgw74  3374/tcp
    sapgw75  3375/tcp
    sapgw76  3376/tcp
    sapgw77  3377/tcp
    sapgw78  3378/tcp
    sapgw79  3379/tcp
    sapgw80  3380/tcp
    sapgw81  3381/tcp
    sapgw82  3382/tcp
    sapgw83  3383/tcp
    sapgw84  3384/tcp
    sapgw85  3385/tcp
    sapgw86  3386/tcp
    sapgw87  3387/tcp
    sapgw88  3388/tcp
    sapgw89  3389/tcp
    sapgw90  3390/tcp
    sapgw91  3391/tcp
    sapgw92  3392/tcp
    sapgw93  3393/tcp
    sapgw94  3394/tcp
    sapgw95  3395/tcp
    sapgw96  3396/tcp
    sapgw97  3397/tcp
    sapgw98  3398/tcp
    sapgw99  3399/tcp
  • Save the file and restart your application (rebooting the machine shouldn’t be required)

Strictly speaking, you should only really one or two of these—the one that corresponds to your SAP system—but I don’t think it hurts anything to have them all in there.

Other Things To Try

If that doesn’t fix it, you might also make sure you’re using a hostname (not an IP address) and that you are using the right connection for your situation (ashost/application server host vs. message server host else there is).

I also stumbled across a user reporting an issue with tabs vs. spaces. I’ve not had any trouble with spaces but your mileage may vary.